The march is the biggest gay pride event in Europe

But the change will not apply to officers serving in Scotland, Dyfed-Powys in Wales, and eight forces in England, where the respective chief constables rejected the request.

The National Pride Parade, together with Pride in the Park, is the biggest annual gathering of gay men and women in Europe.

Until now, off-duty police have only been allowed to attend the event in civilian clothes, but this year 50 gay officers in full police uniform will head the march.

The Gay Police Association said this will send out a signal that it is perfectly acceptable to be gay and in the police service.

Hypocrisy

But it has criticised the reasons given by some forces for rejecting a change.

Stephen Warwick, deputy chairman of the Gay Police Association, said it was hypocrisy given that many forces have for the past three years had officers in uniform at police recruitment stands at the event.

He said: "The Association of Chief Police Officers for Scotland (ACPOS) said its decision was due to legal reasons as Scottish officers have different powers and act under a different legal framework to English officers.

"But officers from foreign countries may attend and some Scottish officers took part in the recent Golden Jubilee parade in London.

"I think this is a mere smokescreen. That excuse certainly can't be used by forces in England and Wales, yet some of them have also refused.

"Dorset said that to allow gay staff to attend in uniform was no different from permitting officers to march in uniform with the Countryside Alliance.

Police forces have been recruiting at the event for the past three years

"I totally reject that. This is not about politics. This is about identity."

A spokesman for Dorset Police said: "It is the general policy in Dorset that any officers attending any such public event involving a march or parade would not be wearing uniform unless they are policing the event."

He added that such matters were constantly under review.

Hampshire Police also rejected the request. Chief Constable Paul Kernaghan said he was sympathetic to the objectives of the National Pride Parade, but that officers should never wear uniform except whilst on duty.

'Neutral body'

He said: "The police are a neutral body and must always be seen in that light by the general public.

"I feel everyone should feel free and confident to support lawful causes.

"However, I reiterate my view that participation in uniform could undermine the traditional neutrality of the police service."

A spokesman for the Police Service of Northern Ireland said he was not aware of any formal request being made for its officers to be allowed to take part in the event in uniform.