Four more people, including two serving police officers, have been detained in connection with an inquiry into alleged bribery and fraud linked to the Police Federation of England and Wales.

The City of London Police, as the lead force for fraud investigations, confirmed the arrests of two men and two women at an address in Leatherhead, Surrey, on Tuesday.

Both women are in their 50s; one was held on suspicion of bribery, fraud by abuse of position of trust, and fraud by failing to disclose, while the other was arrested on suspicion of fraud by abuse of position of trust.

A man aged in his 50s was detained on suspicion of bribery, fraud by failing to disclose, and fraud by abuse of position of trust. A man in his 40s was arrested on suspicion of fraud by abuse of position of trust.

All four were brought to a police station for questioning.

Detective Superintendent Jim Halkett, of the City of London Police’s domestic corruption unit, said:“Our investigation continues to make significant progress, with officers working through a number of lines of inquiry to establish the full facts and circumstances surrounding this case.

“We would like to thank everyone who has already come forward with information. This has been valuable and continues to play an important role in helping us move our inquiries forward.

“This remains a complex and high-profile investigation, and we recognise the public and media interest in it.

“With criminal proceedings now active, we ask that media take care with their reporting and avoid speculation that could impact future court proceedings.”

It comes after officers arrested Mukund Krishna, the former chief executive of the federation, and two other men, a 51-year-old man from Wales and a 55-year-old man from Bristol, in March as part of the probe.

Mr Krishna was suspended from his role in March and he and two other men were later bailed until September.