The latest protest is to coincide with the weekly Cabinet meeting

The cars, emblazoned with posters, are being driven to Whitehall to coincide with the weekly meeting of the Cabinet.

Driven by members of the Stop Stansted Expansion group (SSE), the cars are due to go on to the central London headquarters of airport operator BAA.

The demonstrators were delivering a shareholders' statutory resolution to BAA.

The resolution is aimed at stopping the company handing free car parking perks to MPs and other politicians thought to be worth more than �1m a year.

'BAA desperate'

In mid-December the government is due to publish its aviation White Paper which will say exactly which airports are to be expanded to cover aviation needs for the next 30 years.

It is thought the Treasury favours expansion at Heathrow and Gatwick airport.

But it has also been suggested that a third, extra runway at Heathrow has been ruled out on environmental grounds, with another runway at Stansted preferred instead.

SSE spokesman Brian Ross said: "BAA is desperate for government endorsement of its plans for more runways at Stansted and elsewhere and also desperate to avoid a challenge to its monopoly position in south-east England through its ownership of Heathrow, Gatwick and Stansted."