A Midland MP has put herself on collision course with her own party by rejecting calls for a ban on new airport runways.

Lorely Burt, Liberal Democrat MP for Solihull, has defied the party by saying she wants to leave the door open for the expansion of airports such as Birmingham Airport, which published proposals for a second runway last year.

She is to take on activists who want future governments to allow "no net growth" in runways, in a debate at the party's conference in October.

The runway ban is to be included in the party's pre-manifesto, launched by Lib Dem leader Nick Clegg.

This is an early draft of the General Election manifesto for next year's poll.

It is due to be debated at the conference, to be held in Glasgow, where policy proposals will be put to a vote.

Ms Burt, Parliamentary Private Secretary to the Chief Secretary to the Treasury, Danny Alexander, is to propose an amendment to strike out the ban and highlight the importance of airports outside London for regional jobs and growth.

However, she is likely to face opposition from activists who argue that preventing new runways will protect the environment.

Writing for the Birmingham Post, Ms Burt said the Lib Dems' ambitions for a greener future "must also fit with our vision for a stronger economy and a fairer society".

"It would be short-sighted of us to rule out new routes for airlines offering a chance to explore new markets and encourage investment," she added.

"There is a real chance we risk prejudicing decades of growth by nailing down excessively restrictive plans for airport growth now."

Birmingham Airport last year published plans to build a second runway, allowing it to expand into a truly global airport capable of dealing with 70 million passengers each year - as many as Heathrow handles now.

The proposals were submitted to the Airports Commission addressing a shortage of capacity in the UK.

The commission last year decided not to shortlist proposals for expanding Birmingham but said there was likely to be a case for considering the airport as a potential option for expansion by 2050.

Under the plans submitted to the commission, the airport would also have an additional terminal and see up to 500,000 take-offs and landings annually.

The plan has a heavyweight coalition behind it, with business leaders, local councils and MPs all firmly on board including MP Mark Garnier (Con Wyre Forest), Birmingham City Council and Birmingham Chamber of Commerce Group.

An Aviation Commission set up by the Government is considering whether to allow a new runway at Heathrow or at Gatwick Airport.

Birmingham Airport has urged the commission to give a greater role to airports in other parts of the country.