According to this publication by Transparency International, the UK does not criminalise influence peddling as such. Rather, "the following legislation and regulation may provide some protection against aspects of the relevant corrupt behaviour:
- The Bribery Act 2010 would apply if the beneficiary was carrying out illegitimate activities to influence the public official.
- Political donations are regulated by the Political Parties, Elections and Referendums Act 2000."
Most examples would fall under the Bribery Act, which covers:
All four offences: offering, promising or giving
a bribe to another person; requesting,
agreeing to receive or accepting a bribe from
another person; bribing a foreign public
official; and a corporate offence of failing to
prevent bribery. The Act could potentially be
used to sanction political bribery if giving or
receiving a financial or other advantage in
connection with the "improper performance"
of a position of trust can be argued.
They further note that:
The 2013 Implementation Review Group UNCAC report assessed that regarding trading in influence, the general offences in the Bribery Act 2010 are broad enough to cover most circumstances related with the behaviour in question. The Bribery Act 2010 may be used to prosecute political bribery if the giving or receiving of a private benefit was connected with the improper performance of a “relevant function or activity”. It can also apply if the offer of a bribe is not taken; if the bribe giver knows that acceptance of the bribe would constitute improper performance. It is punishable with a maximum of 10 years’ imprisonment.
While there have been some convictions under the Bribery Act, both of public officials and of private sector workers, as far as I know, there have not been any high profile influence peddling cases so far. Neither of the 2009 and 2010 "cash for influence" scandals resulted in criminal charges (though both resulted in suspensions from parliament), but both predate the Act. A 2015 "cash for access" scandal involving Malcolm Rifkind and Jack Straw resulted in an investigation by the parliamentary standards watchdog (which cleared both of them) but not a criminal investigation. However, a TI opinion piece argued that it showed a gap in UK law regarding influence peddling.