Raids on three suspected London squats ahead of the royal wedding were "disproportionate", a Labour MP says.
They seemed to be "some form of pre-emptive strike" before the ceremony, said John McDonnell, who represents Hayes and Harlington in west London.
Twenty people were arrested in Hackney, Camberwell and Sipson on Thursday.
The Metropolitan Police (Met) said it brought forward the operation because of the royal wedding, but stressed it was not directly related to the event.
This week it indicated it would take pre-emptive action to stop people coming to central London on Friday to cause trouble.
'Abuse of power'
Officers held 19 people at Camberwell Road in Camberwell, south-east London, for allegedly abstracting electricity.
The other was detained at Lower Clapton Road, Hackney, east London, over suspected disorder following the anti-cuts protest in London in February.
An address in Sipson, near Heathrow Airport, west London, was also raided but nobody was arrested.
This was in Mr McDonnell's constituency and he said police had handcuffed one person before they "forcibly detained" others.
"I believe this disproportionate use of force is unacceptable, he told the Commons.
"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."
A group of squatters who had been growing vegetables on the site said some members had been handcuffed before police had left empty-handed.
"The police claim it is all nothing to do with the royal wedding even though the wedding date is tomorrow," said Grow Heathrow spokesman Joe Rake.
"It is such an abuse of their power," he added.
"Let's hope the cost of the whole operation is not being added to the royal wedding budget, which is all being paid for by the taxpayer."