The latest series of hearings in the public inquiry into undercover policing is due to begin on Wednesday.

Witnesses including Piers Corbyn and Lord Peter Hain are expected to give evidence during the next three-and-a-half weeks, during which the inquiry will focus on police activity between 1973 and 1982.

The Undercover Policing Inquiry (UCPI) was set up in 2015 to look at the activities of two shadowy police units after condemnation of undercover tactics.

A public outcry was sparked when it was revealed that women had been tricked into sexual relationships with undercover officers and that police spies had used the identities of dead children without their families’ permission.

Family justice campaigns, including for murdered teenager Stephen Lawrence, were spied upon; and there are claims that some officers were arrested or prosecuted for crimes under fake identities, leading to alleged miscarriages of justice for their co-defendants.

The two units being examined are the Metropolitan Police’s Special Demonstration Squad (SDS), which existed between 1968 and 2008; and the undercover part of the National Public Order Intelligence Unit (NPOIU), which existed between 1999 and 2010.

This batch of hearings will begin with opening statements from parties involved in the inquiry, including counsel to the inquiry itself David Barr QC, then lawyers for the Met Police and the Home Office.

Counsel for those spied upon will also make opening statements, before evidence hearings begin next week.

Witnesses include Mr Corbyn, the brother of former Labour leader Jeremy Corbyn, who was spied on for nearly 20 years after he joined a squatting movement for affordable housing in 1971. He is due to give evidence on April 28.

Lord Hain was a leader of the anti-apartheid Stop the Seventy Tour campaign, which aimed to stop the all-white South Africa cricket team touring the UK in 1970, and to disrupt a tour by its rugby team in the winter of 1969/70. He is due to give evidence on April 30.

The mammoth inquiry has cost more than £36 million to date, although Tory peer Lord Moylan estimated last week that this could rise to £100 million, including police costs, by the time the inquiry reports in 2023.

UCPI hearings are being scheduled in sections by date order, with the first in November 2020, looking at the SDS between July 1968 and around the end of 1972.

During that batch of hearings it was revealed that one undercover officer trained as a clown, while another reported on a charity jumble sale.

The next phase of evidence hearings looking at SDS managers between 1968 and 1982 is due to begin on October 5.

Dates for future hearings have yet to be announced.