The West Midlands MP who was part of Gordon Brown’s inner circle has insisted: “The Prime Minister can get tetchy, but he has never bullied anyone”.

Tom Watson (Lab West Bromwich East) defended his former boss as the row over Mr Brown’s alleged bullying of staff overshadowed his election “fightback”, launched in the region this weekend.

Mr Brown was in Coventry on Saturday urging party activists to believe they could still win a general election, but attention has focused instead on claims he pulled a secretary from her chair, shoved an aide and frightened Number 10 staff with four-letter rants.

Conservative leader David Cameron called for an inquiry into the claims after the founder of the National Bullying Helpline revealed it had received calls from anxious Downing Street workers.

But Mr Watson insisted the claims, published in a book by journalist Andrew Rawnsley, painted a false picture of the Prime Minister.

The MP said: “He gets impatient when things aren’t done. But in all the years I have known him, I have never seen him bully anyone.

“I have never seen him shout at people. I have seen him raise his voice, but not shout. This was with other politicians, not with staff.

“The most I would say is that he gets tetchy. He would never behave in an improper way.

“He was my boss and I would never have put up with being bullied if that had happened.”

Mr Watson has been close to Mr Brown since before becoming an MP in 2001, and the Prime Minister, who was then Chancellor, supported him when he applied to become Labour candidate in the Black Country seat.

Until leaving the Government in June last year, Mr Watson was based in the heart of Mr Brown’s Downing Street operation. He was one of 30 people, including the Prime Minister, based in a large open-plan office in the lower levels of Downing Street, informally known as the “war room”. Liam Byrne (Lab Hodge Hill), a senior Treasury Minister, was also based there.

“I would come in at 8am but Gordon would be there before me. It was very busy and a lot of hard work.

“It couldn’t have operated if the bloke in the middle of the room was bullying everyone.”

The Charity Commission announced it was investigating the National Bullying Helpline following claims it breached the confidentiality of its users by revealing it had received calls from Downing Street staff.

And Professor Cary Cooper, a celebrated expert on workplace stress, resigned as a patron of the charity.

The Prime Minister’s Spokesman insisted he enjoyed working with Mr Brown.

He told journalists: “The Prime Minister has spirited discussions with lots of colleagues, including me.

“I personally find the Prime Minister a very engaging and interesting person to work with.”