Scotland Yard has raided five squats in London 24 hours before the royal wedding – a week after promising pre-emptive action to ensure the day is trouble free.

Three squats in Camberwell, south London, were raided on Thursday morning along with a community at Heathrow, known as Transition Heathrow and set up in opposition to the building of a third runway. The fifth squat raided was Offmarket in Hackney, north-east London.

Scotland Yard said 14 people were arrested in Camberwell. A spokesman denied the raids had anything to do with the royal wedding. Police said the raid at a squat known as Ratstar in Camberwell was carried out under a section 18 warrant to search for stolen goods.

A spokesman said once officers arrived at the address they found that those inside were bypassing the electricity meter and were arrested for "electricity abstraction".

"It's business as usual," a spokesman said. "This is nothing to do with the royal wedding."

On Wednesday police officers from the Metropolitan and Sussex police forces raided a squat in Brighton and arrested seven people.

Sussex police confirmed it had been assisting the Met in executing three warrants in the city in response to the trouble at last month's anti-cuts protest in London, which followed the TUC march in the capital.

Scotland Yard's denial that the raids were in any way linked to the police preparations for the royal wedding came a week after senior officers made clear they would be taking pre-emptive action, including raiding squats and making arrests, in advance of the wedding to ensure that no criminal activity took place on the day.

To arrest people under conspiracy laws the police would have to have evidence of a plot. But the raids on Thursday all appeared to have been carried out under warrants to search for either stolen goods or to look for evidence relating to the disorder at the TUC march on 26 March and the anti-cuts demonstration in London last December.

The warrant issued in Hackney stated the raid was taking place under "section 8 of the Police and Criminal Evidence Act" to look for "documentation ... material ... mobile phones, cameras and correspondence ... that can be linked to events and suspects of serious disorder at the TUC rally on 26 March 2011".

One legal source pointed out that it was highly unusual for so many raids on squats to be carried out in one day. "The Heathrow squat has been there peacefully, supported by many people in the community, for more than a year," said the legal source.

John McDonnell, the MP for Hayes and Harlington, which covers the Heathrow squat, accused the police of "harassing environmental campaigners".

McDonnell raised a point of order in the Commons to question the timing of the incidents, saying they appeared to be "some form of pre-emptive strike before the royal wedding".

He added: "I believe this disproportionate use of force is unacceptable and I would urge that a minister comes to this house from the Home Office to explain what is exactly happening today, what are the grounds for that action and also to contact the Metropolitan police commissioner to explain that many of us feel that this is disproportionate and no way to celebrate this joyous wedding."