A prospective parliamentary candidate who hopes to grab Ann Keen's seat in the House of Commons has called for her resignation, claiming her loyalty to the Government prevents her from acting on behalf of constituents.

Brentford ward councillor and leader of Hounslow's Liberal Democrats, Andrew Dakers, first tried to question MP Keen at a meeting she organised recently to discuss airport expansion, but he said she would not engage with him.

However, Mrs Keen came back to say she was having a personal conversation with a constituent and told her political rival she looked forward to an apology for "so rudely interrupting them".

In a letter Coun Dakers put his question to the Brentford and Isleworth Labour MP again, claiming her closeness to the Government had caused "significant frustration" among residents who wished she would speak out against issues such as the Iraq war and Heathrow expansion.

He said: "The question on many people's lips is whether you will follow in the footsteps of your esteemed and sadly departed colleague Robin Cook and publicly signal your potential resignation from the Government at a point where this could have an impact and plainly alert the Prime Minister to the public discontent and fears around this impending decision."

He added that the Government's plans to build a third runway at Heathrow had been presented in the public consultation document as a "foregone conclusion" and accused the MP of not having "yielded any meaningful results in convincing the Government to retreat from the plans."

Mrs Keen, who last year was appointed as parliamentary under-secretary of state for health services by Gordon Brown, said: "I am sure that anyone with even a limited amount of common sense would understand and accept that my close connection with Government gives me an enhanced opportunity to ensure that my views are listened to."