Diplomatic immunity: Rape accused among nine suspected of serious crime
An embassy official accused of two rapes - one of nine diplomats who faced serious allegations last year - was able to leave the UK without trial.
The suspect, also accused of attempted rape, was among about 23,000 foreign officials entitled to immunity from prosecution, MPs have been told.
The accused had been expelled after their home country had refused to waive immunity, the foreign secretary said.
Others were accused of blackmail, a gun plot, sex assault and driving offences.
Under the 1961 Vienna Convention, designed to allow officials to represent national interests even in hostile overseas regimes, diplomats are not "liable to any form of arrest or detention".
Foreign Secretary Jeremy Hunt told MPs in a written statement: "The [Foreign and Commonwealth Office] does not tolerate foreign diplomats breaking the law.
"When the police bring instances of alleged criminal conduct to our attention, we ask the relevant foreign government to waive diplomatic immunity where appropriate."
When waivers were refused, the UK government requested "immediate withdrawal" of the diplomat involved, he added.
It was revealed last year that embassy staff owed £105m in London congestion charges, while £327,962 in parking charges were also outstanding.
In his statement, Mr Hunt said the number of alleged serious crimes committed by diplomats was "proportionately low".
Police reported 12 claims of serious offences - those carrying a potential jail term of at least 12 months - to the Foreign Office during 2017, the same number as for 2016.
One official each from Finland, Sierra Leone and Saudi Arabia were reported for driving without insurance, while diplomats from Austria and the Commonwealth Secretariat were accused of drink-driving.
A Cambodian official was reported for "carrying a firearm with intent to injure", while an Egyptian diplomat was accused of blackmail and an Algerian faced sexual assault claims.
The nationality of the diplomat accused of rape was not revealed to avoid wrongly identifying colleagues in the country's small overseas mission.