Gordon Brown has been forced to defend Harriet Harman, the deputy party leader, after she wore body armour to tour her South London constituency.

The Prime Minister said that Ms Harman had donned the stab-proof vest only because she was on patrol with officers to highlight neighbourhood policing.

Ms Harman claims that she did so as "a matter of courtesy", and compared it to wearing a hard hat while visiting a building site or a hair net in a meat factory.

Mr Brown was asked at his regular Downing Street press conference whether Ms Harman should wear one when she next visited No 10. "When Harriet Harman went out with the neighbourhood policing unit, she was working with them and that is why she was wearing what she was wearing," the Prime Minister replied, unsmiling.

"She was emphasising the importance we attach to neighbourhood policing in the community. Although crime has gone down and the number of police has gone up and although violent crime has come down 30 per cent, people want to know that they can feel safe when they go out at night or even go out during the day, and one of the things that reassures them is that we are policing in the community; a visible presence there for all to see."

Ms Harman is the second senior Labour woman to seem to imply that London is dangerous for women, after Jacqui Smith, the Home Secretary, suggested that she would not feel safe walking any London street at night.

Ms Harman, meanwhile, mounted her own defence on BBC Radio 4's Today programme this morning, when she described how she had met the officers in their canteen to discuss their work over a cup of tea. "Then we went out on the streets and they hitched on their stab vests, I think is what they are called," she said.

"They were telling me about their new version, [which is] much lighter than the old one so that if they have to chase criminals they can do it much more easily and it doesn’t weigh them down. And they gave me and my assistant [vests] to wear as well."

It was Ms Harman's assistant who took the photograph which has since been widely published. Ms Harman said her gesture had been misinterpreted. "It was just a courtesy, there was no security issue whatsoever, it was almost like wearing the kit when you go out with the team," she said.

"I don’t have to wear a stab-proof jacket and I didn’t have to wear stab-proof jacket. I put it on just as a matter of courtesy and because I was going out with the team."

The Opposition has seized on the gaffe, insisting that Labour's policies on crime had indeed made the streets of London too dangerous for women.

David Cameron said he thought that large parts of London were not safe, although he predicted that Ms Harman would live to regret her decision to wear the jacket.

"I don’t think it’s a very sensible thing for the Leader of the House of Commons to be walking around her constituency in a stab vest," the Tory leader said. "I think when she looks back she will rather regret putting the stab vest on."

David Davis, the Shadow Home Secretary, said: "Under Labour, London has become one of the most dangerous cities in the world and the minister, like the Home Secretary before her, clearly knows it. You would not need body armour in New York, Paris or Tokyo."

Boris Johnson, the Conservative candidate in the elections for the Mayor of London, agreed: "The simple fact is that 27 teenagers were killed last year and a further 11 so far this year. Londoners do not have the luxury of personal police protection or stab-proof jackets which is why I have put tackling crime at the heart of my campaign."

Camberwell residents, however, sprang to the defence of their MP. On the Camberwell Online blog, Hannah writes: "I think the reports about HH are slightly unfair - from personal experience if, as a civilian, you go for a walk about with the Police and they routinely wear stab vests [as the Met do] they will ask you to wear one for health and safety reasons - I had to wear one when walking around Swindon at night with the police last year."

On the same blog Dagmar agreed, blaming the media for whipping up controversy. "Exactly, Hannah. The Today programme is all huff & puff," she writes. "An MP just has to walk outside to breathe the air and Humphrys is upon her like Basil Fawlty, 'You are, are you not, an air head?' There is always some johnny trying it on."

PeteW says: "It’s not a sentiment I’d usually express, but poor old Harriet. Still, she gave a particularly grumpy John Humphrys a decent fight. I’d still guess she wishes she’d never put on the vest, ‘courtesy’ or not."

Other bloggers were less tolerant. "Stupid fearmongering publicity stunt," mocked blogger Nothing Is True, in a post on the Godlike Productions website.

Veritas told Yahoo answers: "Perhaps she should be going around in a Sherman Tank rather than stab-proof vest. She has got to be one on the most loathsome of this Labour Government's feminist harridans."

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