The change is a relaxation of rules that were brought in after the 2008 financial crash.

The government has also targeted a major Indian energy company and Chinese oil terminals in new sanctions.

Vet prices have risen at nearly twice the rate of inflation, the Competition and Markets Authority found.

The chancellor also said she was considering further measures on public spending, in a bid to put the UK's finances on a firmer footing.

It is the third-largest fine the communications watchdog has ever issued.