Paul Nuttall has urged Mark Reckless to resign as a Welsh AM
Mr Reckless, who defected from the Conservatives to Ukip in 2014, will now sit with the Conservative group in the Senedd after quitting the eurosceptic trailblazers.
The 46-year-old was elected under the Assembly’s list system, which means there can be no by-election as seats are won on a party-basis as opposed to winning a personal mandate.
Nobody elected Mark Reckless, they elected a Ukip AM
Paul Nuttall MEP
Mr Nuttall told the Express.co.uk: “I’m disappointed Mark has left, but let’s not forget Mark was elected on a list system in South East Wales.
“Nobody elected Mark Reckless, they elected a Ukip AM and therefore I think Mark should stand down and pass it onto the next person on that list.”
Mr Nuttall slammed Mr Reckless’ reluctance to relinquish his seat, adding: “He did the honourable thing back in 2014. When you leave a party and join another, I think you should call a by-election.
Douglas Carswell and Mark Reckless both defected to Ukip from the Tories
“Obviously you can’t do that in this situation because it’s not like a Westminster parliamentary seat where you elect an individual… he doesn’t have a personal mandate, he has a Ukip mandate.
He added: “But it’s his choice. I know what the honourable thing to do would be, but we’ve had this happen to us before with MEPs who were elected on a list system in the European Parliament.
“I just think the honourable thing to do if people elect a party and not a person, then you really have a duty and let the next person on the list stand up.”
Mr Nuttall confirmed he had not spoken to Mr Reckless about his about his intention to leave Ukip or since the formal announcement.
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All the pictures from Stoke Central by-election Thu, February 23, 2017
Voting has begun in the Stoke-On-Trent Central by-election which was called after sitting Labour MP Tristram Hunt resigned from his seat to be a museum director. The seat has always been a Labour stronghold but will see fierce competition from UKIP as they target people who voted for Brexit and the tradtional Labour working classes
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Labour candidate Gareth Snell celebrates with his wife Sophia (right) after winning the Stoke-on-Trent Central by-election
The MEP said he should have anticipated such event following Douglas Carswell’s resignation – another former Tory MP who switched to Ukip and has now left the party.
He said: “Douglas and Mark are very close. When Douglas left, I suppose we should have saw this coming.”
Mr Reckless’ move back to the Tories does not appear to have been welcomed with open arms, as Gower’s Tory MP Byron Davies said it was “not a particularly bright idea” to let him back into the group.
Andrew RT Davies, the Welsh Conservative leader, told the Express.co.uk that Mr Reckless had not applied to officially rejoin the Conservative party but will sit as a Conservative AM.
Mr Davies said: “Mark has not applied, or tried to apply to be a member of the Conservative party, but this is a voting arrangement to work as part of the Conservatives in the Welsh Assembly.
“We will obviously form the second largest political group in that Assembly and we will carry on doing the job people put us there to do which is put the Labour government to account."
Mr Nuttall said that it appeared as if Mr Reckless was in political “limbo”.
He added: “It looks as if Conservative central office aren’t that keen to have him as a member. That’s a problem for Mark to sort out now… I’m just sad it’s ended in this fashion.
“Neil [Hamilton, the Welsh Ukip leader] feels bitterly let down, as do all the other AMs, as do the membership in Wales. But as I say, this is chip paper. It’s news today, gone tomorrow.”
Despite recent high-profile defections, Mr Nuttall insisted his party was not in crisis.
He said: “Our membership has continued to grow. I don’t think we are a party in crisis in that sense. We always knew we were going to go through a tough period with Theresa May enjoying this extended honeymoon, but it won’t last.
“I’ve read the obituary of Ukip more times than I’ve had hot dinners and we always come back and we always come back stronger.”