A REMAIN backing minister who dramatically resigned in protest over Brexit was secretly investigated for bullying, The Sun can reveal.

Pro-EU Welsh MP Guto Bebb walked out as a Defence Minister on Monday evening blaming concessions given to Brexiteers for his anger.

However he has also faced “serious allegations of bullying” that have been probed by Conservative HQ’s Code of Conduct panel.

But party chiefs are refusing to publish their findings, prompting allegations of a cover up.

Yesterday Conservative Party staff confirmed that they had recently concluded an investigation into Mr Bebb, with one worried official describing the claims as “explosive.”

But they refused to publicly comment on the matter and said only the complainants would be told the outcome of the probe.

However The Sun understands that a Tory MP and Welsh party officials have made a number of reports about Mr Bebb’s behaviour and none of them had yet been informed about the conclusions of the investigation.

One senior Tory MP told The Sun last night that “it was no secret that some Welsh MPs do not like each other.”

But another influential Tory grandee hit out: “The party have handled this terribly from start to finish and now it looks like they are trying to sit on the report.”

Late on Monday night Mr Bebb had stunned colleagues by announcing that he was quitting government from the voting lobby of the House of Commons.

And moments later he voted against an amendment put down to the PM’s Custom’s Bill by Leave backing Tories - saying he had no choice but to quit after the PM “caved in” to them.

He did not respond to calls from The Sun.

Last night a Tory source insisted there was no cover up but old The Sun that the party's ruling board had asked for more time to probe the allegations despite the initial investigation finishing.