Image copyright Reuters Image caption Some of the world's biggest banks have been accused of colluding to fix Libor

A former senior trader at Rabobank has pleaded guilty to interest rate rigging in the US.

Paul Robson is the second trader at the Dutch bank to plead guilty to trying to rig the Yen Libor rate and the first Briton to do so.

Last year Rabobank paid $1bn (£597m) to US and European regulators for its part in the global rate-rigging scandal.

Barclays Bank, Royal Bank of Scotland and Lloyds Bank have all previously been fined for rate rigging.

Mr Robson conspired to manipulate Libor submissions to benefit trading positions between 2006 and 2011, the US Department of Justice said.

Libor - London interbank offered rate - is one of the interest rates use by global banks to lend money to each other. It supports hundreds of trillions of dollars of transactions, and is used to set interest rates on credit cards, student loans and mortgages.

Regulators in the US and Europe have been investigating whether banks attempted to manipulate this and other key interest rates to benefit their own trading positions.

Nine people, including Robson, have so far been charged by the Justice Department.

US prosecutors said Robson pleaded guilty to one charge out of the 15 he had faced.

Takayuki Yagami, another former senior trader at Rabobank, in June became the first to plead guilty for his role in the scheme.

Robson worked as a senior trader at Rabobank's money markets desk in London, and also served as the bank's primary submitter for the Yen Libor calculation, the Justice Department said.

'Bigger crooks'

He used his position to submit rates requested by Yagami and other traders, according to prosecutors.

In 2007 Yagami asked Robson by email for a high submission for one of the rates, Robson answered: "no prob mate let me know your level."

After Yagami made his request, according to the Justice Department, Robson confirmed: "sure no prob... I'll probably get a few phone calls but no worries mate... there's bigger crooks in the market than us guys!"

In a statement Leslie Caldwell, who heads the Justice Department's criminal division, said: "The scope of the fraud was massive, but the scheme was simple. By illegally influencing the Libor rates, Robson and his co-conspirators rigged the markets to ensure that their trades made money,"

In July Lloyds Banking Group was fined £218m for "serious misconduct" for its part in interest rate rigging.

Lloyds manipulated both the yen and sterling Libor rates and tried to rig the rate for the US dollar, the Financial Conduct Authority (FCA) and US financial regulators said.

At the time Bank of England governor Mark Carney called the misconduct "reprehensible".