By Jane Mower BBC News, London

With average house prices in London standing at �302,000, prospective buyers must earn an average �75,500 a year in order to become a homeowner.

How crucial is key worker housing?

The outlook is bleak for most but for key workers on low wages, buying a home can be almost impossible.

Many face leaving the public sector in search of more money or leaving London to find cheaper homes.

So is enough being done to help key workers and what would the main parties do to make a real difference?

Currently, housing assistance is offered to key workers, including nurses, police officers and teachers, in the form of �50,000 loans, shared ownership schemes and properties for rent at affordable prices.

In London the mayor has to meet a target of providing 23,000 new homes every year until 2006 - 50% of which should be affordable homes.

There is a lack of housing and a lack of will by a succession of governments to pour the sort of money into housing that is needed Dee Doocey, Liberal Democrats

James MacPherson, director of Notting Hill Home Ownership at the Notting Hill Housing Group, said that "prospects for key workers in London are on the whole positive".

"Schemes have provided much needed homes to thousands of essential key workers who keep our city alive."

But he said the definition of "key worker" still needs revision as within guidelines relating to eligibility, definitions "are drawn too tightly and allow for little flexibility".

He also said that the needs of the lowest paid key workers, such as nurses, are not being met.

Living costs

Stamp duty has proved to be a hot topic in this election with Labour doubling the stamp duty threshold to �120,000.

The Conservatives have now pledged to wipe out the tax on buying homes valued up to �250,000 and the Liberal Democrats want the limit raised to �150,000.

Although these policies go some way to helping key workers there is much more that needs to be done to help those in London faced with higher house prices and living costs.

BBC News has taken a look at what the three major parties propose to tackle the problem.

Tony Arbour, Conservative spokesman for planning and housing on the London Assembly, said the emphasis should be on affordable housing for people to buy and giving assistance to those who want to do just that.

"The most obvious way of doing this is to ensure the share of equity, or escalator, with which people can buy is as low as possible," he said.

"Planning requirements for affordable housing provision should ensure properties be for sale rather than for rent.

"And thirdly employers should be helping to provide housing for key workers by working with local councils."

Minister for London and Housing Keith Hill said providing affordable housing for key workers was of "critical importance".

"Quite clearly the government is very aware of the housing pressures which are in some cases forcing workers in the key public sector to move out of London," he said.

"We have to provide this assistance to key workers in order to retain services and draw people into London."

Mr Hill said their policies were "more than meeting the needs of key workers" but they were extending the schemes to offer assistance to more people.

Liberal Democrat spokeswoman and chair of the London Assembly's economic development and planning committee Dee Doocey said the situation is "desperate".

"There is a lack of housing and a lack of will by a succession of governments to pour the sort of money into housing that is needed."

She said the Lib Dems would seek to bring thousands of properties standing empty in London back into use and to ensure landlords rent them out at affordable rents.