The army will no longer readmit troops sacked for taking illegal drugs as part of a zero-tolerance policy, Gavin Williamson, the UK defence secretary, has announced.

Soldiers who had failed drugs tests had been allowed to rejoin the armed forces so long as they passed new examinations. But on Saturday Williamson said the use of drugs is “incompatible” with military service and there would be no more readmissions of former users.

The announcement follows reports this summer claiming that a shortage of troops had led to repeated drug offenders avoiding dismissal. It also emerged that five-figure financial incentives had been offered to a handful of former service people to rejoin in specialist roles.

The Ministry of Defence was forced to defend the readmissions since the scheme began in April “to fill highly skilled or specialist roles” where there was a “clear need”.

According to the Mail on Sunday, the number of soldiers caught taking drugs rose from 570 in 2015 to 730 in 2016.

Williamson said the new approach was the only way to ensure “high standards are maintained” throughout the British military.

“The misuse of illegal drugs can cause terrible damage to people’s lives and their purchase fuels organised crime, both in the UK and across the globe,” Williamson said.

New recruits will also receive better education about the consequences of the misuse of drugs under the new approach.