Patrick Mercer resigns as Conservative MP for Newark – and Nigel Farage says he may fight for seat in by-election

The former MP was banned from Parliament for six months on Tuesday

Ukip leader Nigel Farage, left, says he may contest Patrick Mercer's former Newark seat in a by-election (Getty Images; PA)

David Cameron faces a damaging by-election defeat after a former Conservative MP dramatically resigned from the Commons over sleaze allegations.

Patrick Mercer announced he was quitting as the MP for Newark, Notts, following accusations he broke parliamentary rules over lobbying.

Nigel Farage, the leader of the UK Independence Party, signalled he was considering whether to stand in the by-election which is likely to take place in June.

The Tories – already facing coming third in next month’s Euro-elections – would face an uphill struggle to hold on to the seat.

Mr Mercer decided to resign after learning he faced a six-month suspension from Westminster as punishment for his behaviour. The penalty was agreed by the Commons standards committee and was due to be formally announced tomorrow.

Mr Mercer, who has sat as an independent since quitting the Tory whip 11 months ago, last night said he accepted the committee’s verdict and apologised to his constituents for his conduct.

The former army colonel won Newark from Labour in 2005 – partly helped by the sitting MP facing allegations over her expenses – and built up his majority to 16,000 at the last election.

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Ukip came fourth with less than four per cent of the vote, but the backlash against Mr Mercer could turn the by-election into an attractive prospect for the anti-European Union party. It is certain to create a headache for Mr Cameron, who is braced for the Tories to be outpolled by Ukip and Labour in the European parliamentary elections on May 22.

Mr Farage indicated yesterday that he could stand as long as the contest takes place after the Euro-elections. He said: “I will give it serious consideration.“

In a statement outside the Commons, Mr Mercer said: “It is clear to me the constituency of Newark needs to be represented properly. I will not argue with the findings of the committee and I can only humbly apologise.

“My military background has taught me that you must never let down the people who depend on you, and those people are my constituents of Newark. If that becomes the case, you must go without any argument.”

Mr Mercer secretly filmed by reporters last year apparently accepting £4,000 to lobby on behalf of Fiji, which faces accusations of human rights abuses.

He apparently agreed to set up a parliamentary group to press for the south Pacific nation to return to the Commonwealth.

Ahead of last year’s report, Mr Mercer announced he was referring himself to the Parliamentary Commissioner for Standards. He also said he was resigning the Tory whip and had decided not to stand at the 2015 general election.