Daniel Sandford BBC home affairs correspondent

The idea of a unified frontier force - which the government has been criticised for being slow to create, in a report by the Home Affairs Select Committee - has been around for some time now.

The committee first suggested it in its Border Controls report in January 2001.

The plan was to bring together parts of the police, Customs and Excise and the Immigration Service to form a single organisation to police our borders.

The government's first response was that it was not convinced by the proposal, but ministers promised to look at it more closely.

In September 2003, Home Secretary David Blunkett confirmed that a cabinet committee was urgently considering whether to bring together all those involved in border control - including Customs and Excise, the National Crime Squad, the National Criminal Intelligence Service, the coastguard and police special branches.

MPs want various agencies to work together to protect UK borders

"My own view", he said, "is that there will have to be change. We have not yet agreed that change... We do not want to set up something which works on paper but does not actually work in practice."

Meanwhile rumours continue to circulate of an occasionally angry turf war between the various agencies.

In their latest report, the MPs of the home affairs committee are blunt.

"It is now time", they say, "for the government to resolve the disagreements between agencies on this proposal and take action to promote their greater integration."

Why is it needed?

Those in favour of a unified force quote an example of a family who were returning from France in a white van.

The all-party group insists Britain is "not a soft touch" but concludes there are weaknesses in the current system UK's border security criticised

They had been on an innocent day trip. They went through immigration. They were then stopped by the Kent Police Ports Unit and asked to unload the van.

It was soon clear they were doing nothing illegal and they were told they were free to go.

They drove 10 yards down the road only to be stopped by Customs, who asked them to unload the van again.

It took them an hour to get out of Dover. It should have taken them five minutes.

As well as inconveniences like that there are more pressing reasons for greater integration.

Intelligence could be shared better.

Each of the agencies operates different computer databases.

British Airways complain that they have had to write three different bits of software to integrate with the systems of the Immigration Service and Customs and the police.

Of course there are places where things work well. But it very much depends on whether the staff from the different organisations happen to get along with each other.

Ad hoc

Policing the UK's borders should not be hard. We are, after all, an island nation.

The only land borders are with the Irish Republic and, arguably, the Channel Tunnel.

Perhaps that is why our controls have developed in an ad hoc manner.

Certainly when faced with the huge numbers of clandestine immigrants in the late 1990s and early 2000s, the old system was found wanting.

That is why MPs have repeated their call for a unified frontier force.