If you saw the hotel doorknob sign which I showed you on last Tuesday's programme, you'll know why I'm writing about Manchester.

We were back on the road again this week, presenting live from Manchester, where they've been holding the annual gathering of Britain's biggest bosses - the CBI conference.

We flew, by the way, because the railways were out of action again - so every plane that weekend from London to the northwest of England was packed with the biggest names in British industry.

Business' A-list

It was quite a gathering.

I counted three cabinet ministers - including the Chancellor, Gordon Brown. His American counterpart - US Treasury Secretary Paul O'Neill - spoke at the conference, and took a tour of the re-developed areas of the city.

The worldwide boss of Ford flew in - and made a fuss about the Euro. The head of BP told us how he'd turned a sleepy British company into one of the world's biggest and best.

Capital cities are always hated. They're always accused of distorting the economy - sucking away money and talent from the outlying regions.

Bosses from Hewlett-Packard, Unilever, the Carphone Warehouse, British Airways, Camelot, Capita, the London Stock Exchange and NASDAQ, were all there - plus senior trade unionists and environmental campaigners.

In business terms, this was a guest list to beat Oscar night.

And they all got a hotel doorknob sign.

Mine was bright pink on one side, and bright orange on the other - quite a contrast from the subtle pastels used to decorate the room.

Banging on the door

The orange side said London commuters spend 3 hours more each week getting to work than people in Manchester. The pink side said office costs were 350 per cent higher in London than in Manchester.

So there was nothing subtle about the message either. This was Manchester telling all the high-powered bosses who'd flown up from London that they should stay after the Conference - and move their businesses up north.

Plenty of our leading firms already have operations in the north west - and more are on the way. Marks & Spencer says it will move its head office finance, payroll and personnel departments to Manchester next February. It's been lured there by lower business costs and the ready availability of office space.

It's a message the local Northwest Development Agency rammed home to its captive audience at the CBI.

It told them they could pay less for their offices - and pay their workers less (average earnings in the north west are 15 per cent lower than in the south east of England).

But that money goes further - the average house buyer in Manchester will pay a staggering �94,000 less for their first home than someone in London. And full time childcare is �50 a week cheaper.

Cheap drinks

They didn't say this in the leaflets, but the drink's cheaper too. While I was safely tucked up in bed, some of my colleagues sneaked out for a night on the town. Over breakfast the next morning, they were still stunned that a round of drinks for half a dozen people cost less than a tenner. You certainly don't get prices that low in London.

So - with the greatest of respect - Manchester, Liverpool, Belfast and all the others should stop whinging about London, and attend to their own knitting.

You hear the same message from other economic development agencies across the country. When I was in Belfast recently, I had a chat over the bacon and potato bread with the people from Invest Northern Ireland. They're trying to lure Dublin-based companies, fed up with the Irish capital's traffic gridlock and soar away house prices.

It's the Manchester-London tussle - but with different names.

Capital offences

Capital cities are always hated. They're always accused of distorting the economy - sucking away money and talent from the outlying regions. And they do. But there's a simple reason they get so powerful. They've got critical mass.

London is the national hub for politics, law, finance, and the media. It has the House of Commons and the House of Lords. It has the High Court and the Court of Appeal. It has the Bank of England, the Stock Exchange, the City banks and Lloyds. It has all the national newspapers, and the headquarters of the BBC and ITV. And on the side, it's got world-famous galleries, theatres and cinemas.

That's not to say other parts of the UK don't have some of these things too. But London has them all, in greater number. That's why big business needs to be there. It's not just the vanity of having a London brass plate. It's functionality - being closer to your shareholders, your customers, your trading partners - and to the money you need to keep going.

And it's why more people choose to live in London - despite the sky-high house prices and the overcrowded Tube. The population of Liverpool fell by more than 3 per cent in the last decade.

The population in the north west of England as a whole didn't change in the 1990s. But London's population is increasing again - after 40 years of decline. And experts say it will grow by another 700,000 in the next 15 years.

So - with the greatest of respect - Manchester, Liverpool, Belfast and all the others should stop whinging about London, and attend to their own knitting. Trying to lure companies away from the capital should only be part of the plan. Places like Manchester and Belfast also need more new businesses - started from scratch by local people.

Existing businesses also need help to do better. The Lancashire West Partnership is planning a new productivity centre - so local firms can boost their skills and copy the best ways of doing business at other companies. Northern Ireland had a similar drive with its Growth Challenge - now it has a Centre for Competitiveness.

And sometimes local firms need to be encouraged to raise their game. Many small companies stop themselves growing - because bosses don't want to deal with investors. They don't want to sell shares to raise cash - or bring in outside money from private backers - because they'd have to hand over some of the business in return. They'd rather stay small - so they can stay in control.

That's fine for the family - but it costs the country jobs and wealth. As Yorkshire, Manchester and Liverpool - the crucible of the Industrial Revolution - can tell us, all big businesses started small. They just thought big.

Declan Curry is Breakfast's regular business presenter, bringing you live updates from the London Stock Exchange every weekday morning from 6am