The mass detention and confiscation of personal cash was carried out last Saturday under schedule 7 of the Terrorism Act 2000, which allows officers to stop and search people for up to nine hours and confiscate material even if there were no previous grounds for suspicion.

According to witnesses, some female passengers were subjected to intrusive strip searches and had their veils removed in front of male police officers. One is said to have fainted in shock. A number were allowed to keep around £30 each as spending money, others said they were left with nothing.

The operation was carried out by the Metropolitan police’s Counter Terrorism Command (SO15). A police spokesperson denied there had been any strip searches, that anyone had been left without any cash or that any of the women had their veils removed in front of male officers.

As many as 26 people are understood to have had money seized and may have to go to court to recover their assets. They will have to persuade magistrates they are not funding terrorists. All of the travellers had British passports or the right to remain in the UK and returned home later in the weekend.

Most, however, did not speak much English. The wrong interpreters, it is alleged, were provided and many women encouraged to sign forms they did not understand.

It is unusual for the police to devote such resources to targeting the Kurdish community. The French demonstration on 11 January was in memory of three Kurdish women activists – including a prominent founder of the outlawed Kurdistan Workers Party (PKK) – who were murdered in Paris a year ago. Kurdish exiles allege that the Turkish state was involved in the killings; Ankara says it was an internal PKK dispute.

Three busloads of demonstrators set off from north London on Friday evening. The third bus, carrying mainly women, was detained for longest; it did not eventually reach Paris until 3pm. “Some women were searched by female officers but their veils were removed in front of male officers,” said Ayse Gul Erdogan, a community worker who was in another coach. “One woman fainted in shock. They confiscated different amounts of money. Some were given about £30 back by the police for their day in Paris.

“Those in the third coach, which had 38 people on board, were made to walk a long way to another building. They were questioned separately. Several of the women had £500 on them but that’s because they like to carry their money with them; they don’t feel safe leaving it at home.”

Aysel Gulser, who was also on the Paris demonstration, took statements from 15 of the women who had been detained. She told the Guardian: “The women said they felt horrible after being searched. They were stripped down to their underwear and said it felt like a sexual assault. One 55-year-old woman had €115 £95 on her; she had been given it by her son. They officers took it away from her but gave €50 back.

“Another couple, who were going to buy presents in Paris, had £350 taken off them and nothing was given back to them. They said they needed money to eat and buy food but the police told them others on the demonstration would look after them.

“The police said that they knew the women were carrying money for the PKK because someone had told them about it. They were trying to make them think there was an informer. We will be taking legal action against the police for this treatment.”

Alastair Lyon, a solicitor with Birnberg Peirce representing those detained at Dover, said: “I anticipate we will be making formal complaints. [Under Schedule 7] it’s designed to happen almost outside the normal procedures where there are legal protections.

“There is no need for the normal ‘reasonable suspicion’ grounds to investigate. This was a bad example of a an oppressive and disproportionate use of the schedule 7 powers. It creates fear among people who feel they are being investigated and have the least legal protection.”

In response to the allegations, the Metropolitan police said: “It was ensured by officers that those stopped retained sufficient funds for their personal needs. A quantity of cash was seized.” No veils were removed in front of male officers and no strip searches conducted, the statement added.

More than 60,000 people were the subject of ports stops conducted in 2012/13 under schedule 7 of the Terrorism Act. David Miranda, the Brazilian partner of the former Guardian journalist Glenn Greenwald, was held at Heathrow for 8 hours and 55 minutes under the same regulations last August.

The legislation is being revised. The home secretary, Theresa May, has asked parliament to limit the powers of schedule 7 through clauses in the anti-social behaviour, crime and policing bill, which is currently going through parliament. The changes will cut the maximum period of detention to six hours and introduce other safeguards.