David Cameron is alleged to have called the former Rochester and Strood Conservative MP Mark Reckless a “fat arse” following his defection to UKIP.

Mr Cameron is reported to have made the remark during meetings with party activists at the Conservative party conference

In comments that appear to underline the deep fury among the Conservatives over the defection, the Prime Minister has also signalled his intent to take a leading role in the forthcoming by-election.

He is said to have told members that volunteers “knocked on doors, stuffed envelopes, licked stamps to get his fat arse on the Commons benches, and this is how he repays them.”

Meanwhile, the Mayor of London Boris Johnson has raised eyebrows over a quip that UKIP defectors are “the sort of people that have sex with vacuum cleaners.”

Referring to the recent ban on powerful vacuum cleaners by the EU, Mr Johnson told a fringe meeting: "And I have read that there are some people – probably the type who are thinking of defecting to UKIP – who present themselves at A&E with barely credible injuries sustained through vacuum cleaner abuse.’

Mr Reckless has acknowledged he is taking a gamble by calling a by-election saying it is a big risk and he could end up as footnote in political history.

He was contacted to comment on the remarks but has yet to do so.

In other by-election developments, the Liberal Democrats are expected to select a candidate to contest the seat on Friday.

Medway council councillor Geoff Juby, who fought the 2010 election, said he would apply for the nomination.

What do you think? Have the political insults gone too far? What does this say of our senior politicians? Are they right to be angry? Join the debate below.