Britain's financial watchdog could intervene if there are too few participants to set commodity benchmarks including gold and silver, a senior official at the Financial Conduct Authority (FCA) said.

U.S. investors and traders have filed almost 20 antitrust lawsuits against the five banks involved in the London gold fix, accusing them of colluding to manipulate the bullion price. --- FCA head of enforcement and financial crime Tracey McDermott said while the regulator would be nervous about stipulating the number of participants needed to set benchmarks on commodities, including for gold and silver, it could step in if there was a threat to the market.

"These (benchmarks) are things that exist for the benefit of the market, so the market should be looking for market-based solutions to make sure it is still viable," McDermott told the Reuters Financial Regulation Summit in London.

"But if there is a risk of dislocation because people are withdrawing and we think that breaches or is a risk to our objectives then we would set that as one of our activities but it is not entirely straightforward."