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Zac Goldsmith has refused to rule out a return to the Conservative party.

In an interview with Sky News the former mayoral candidate said he was “not thinking ahead that far.”

Mr Goldsmith quit as a Tory MP in protest at the Government’s decision to back a third runway at Heathrow.

He tendered his resignation in October triggering a by-election in the south-west London seat.

The Conservative Party said it would not contest the seat, amid claims it did not want to divide the Tory vote, risking a Liberal Democrat victory.

The Liberal Democrats have fielded Sarah Olney in the by-election, which will take place on December 1.

Speaking to Sky News on Sunday Mr Goldsmith refused to be drawn on whether he would consider re-joining the Conservative party, saying his sole focus was winning the by-election.

He said: "Who knows if I will even stand in the next election. It would be the height of arrogance to start putting this one in the bag."

"I could join the Monster Raving Loony Party in five year's time.

"I am not thinking ahead that far.”

Mrs Olney has tried to shift the focus of the debate away from Heathrow and onto Brexit pledging to vote against triggering Article 50, the formal process for leaving the EU, if she is elected.

Mrs Olney also said she would fight for another referendum on the terms of Brexit.

She said: “It’s a second referendum but it’s not re-running the first referendum, it’s very much the next step.”

Other contendents in the Richmond by-election are Howling Laud Hope, Monster Raving Loony Party; Maharaja Jammu and Kashmir, One Love Party; David Powell, independent; Dominic Stockford, Christian Peoples Alliance; Fiona Syms, independent; Christian Wolmar, Labour.