Royal security has been repeatedly questioned

The Independent Security Commission was asked to investigate after the incident.

Its report is thought to recommend "positive vetting" for royal jobs with every aspect of an applicant's life is looked into.

MI5 could take a lead role in checking people's backgrounds.

The Security Service also do this for sensitive jobs in Downing Street, the Ministry of Defence and elsewhere.

The commission was headed by senior judge Dame Elizabeth Butler-Sloss and is now being examined by the Home Office.

The prime minister ordered the investigation after Daily Mirror journalist Ryan Parry was able to get a job as a footman and work for two months with only cursory efforts to check his background.

Mr Parry had worked close to the Royal Family and had access to royal sites in the run-up to a visit by President George W Bush, with security supposedly stepped up.

Concerns had been raised earlier in the year by comedian Aaron Barschak's gatecrashing of Prince William's party at Windsor Castle.

BBC royal correspondent Nicholas Witchell said the actual physical protection of the royals - enhanced in the current climate of fear over possible terrorist attacks - was unlikely to see major changes.