Peterborough's SDP election candidate challenges Nigel Farage support for the NHS as he pushes his pro-Brexit credentials

Former Daily Express political editor Patrick O'Flynn praised his former political ally Mr Farage's "overall contribution to the Brexit cause" but accused him of a "decades-long antipathy to our National Health Service".

Both the SDP and Mr Farage's new Brexit Party are in direct competition for the vote of Brexit supporters at the June 6 by-election following the recall of former MP Fiona Onasanya, after she was jailed for perverting the course of justice.

Mr O'Flynn, who served as economics spokesman for UKIP when Mr Farage was leader, before defecting to the SDP, launched his campaign at the Great Northern Hotel this afternoon (Tuesday) in front of journalists and supporters, where he pitched himself as a centrist, pro-Brexit supporter.

He said it "would have been easy for me to duck out of this by-election to give Nigel's chosen candidate - whoever that turns out to be - a clear run," but that he wanted to offer the people of Peterborough a "credible, pro-Brexit candidate who did not bind them into a full slate of right-wing, Thatcherite views on other issues".

He added: “Over the next few weeks I want to make Nigel do something I know he will not want to do. And that is to drop his decades-long antipathy to our National Health Service, funded out of taxation, organised by the state and free at the point of need.

"To abandon his preference for an American-style, private insurance model of healthcare and to make an unqualified commitment that his Brexit Party will always support the NHS and extra investment into the NHS and oppose its privatisation.”

Mr O'Flynn, who campaigned to Leave at the 2016 referendum, has been based in Peterborough for the past five years while sitting as an MEP for the East of England.

He used his campaign launch to position himself as a champion of the NHS and tough on crime, while also promising to end austerity, but the biggest focus was on Brexit which he used to criticise Conservative candidate Paul Bristow and Labour candidate Lisa Forbes.

Mr O'Flynn added: "Peterborough needs and deserves an MP who is genuinely committed to its overwhelming vote to leave the EU and leave it properly.

"And I note, by the way, that the Conservative Party candidate has still not uttered a word of criticism of Mrs May's surrender document and that the Labour candidate wants to block Brexit altogether."

Taking questions form journalists, Mr O'Flynn said he had chosen an office in Peterborough as an MEP due to its high levels of euroscepticism.

Although currently living in London, he talked up his knowledge of Peterborough and promised to move to the city if elected.

He added: "I have done many events in the city and public meetings at the Key Theatre, here and other venues.

"I'm not someone that will just be parachuted in from outside the city, and I have taken the trouble to meet city leaders on issues such as the National Health Service.

"I've immersed myself in the life of the city have a great affection for it."

Joining Mr O'Flynn was party leader William Clouston, who pitched the SDP as a "distinct" centrist party that had been eurosceptic for the past 30 years.

He claimed Mr O'Flynn joining the party had proved to be a "turning point" with membership then growing "rapidly", while he maintained that his party's policies had all been fully costed

"We've gone from strength to strength and are a party going places," he added.