A British whistleblower who cannot leave Croatia after being arrested says he is "bewildered" as to why the UK government would not intervene.
Jonathan Taylor, from Southampton, gave evidence against his old employer, Dutch oil firm SBM Offshore, in 2012.
In July, the lawyer was arrested on an Interpol red licence issued by Monaco on bribery and corruption charges.
The UK government said there was "no evidence" his arrest was linked to whistleblowing.
Mr Taylor, who provided evidence about bribes being offered in return for lucrative contracts at SBM Offshore, said: "The way I'm treated by the government, whereby it choosing to knowingly sit on its hands and not get involved when it's been invited to get involved, is utterly beyond all logical conclusion and I am beyond myself, bewildered."
He is not facing any charges in the UK and is awaiting the outcome of legal proceedings which will determine whether his extradition to Monaco will be granted, the House of Commons heard on Monday.
Foreign Office minister Wendy Morton told MPs that as there was "no outstanding case" against Mr Taylor, the UK had notified the Croatian authorities that the government was not seeking to extradite him.
The government had also approached the Monegasque Prosecutors' Office to request the details of the charges against him, she said.
She added: "If we receive any evidence that Mr Taylor's arrest is linked to his whistleblowing activities or that due process is not being followed, we will of course consider what further steps we can take to support him."
Some MPs, including Conservative former minister Caroline Nokes, for Romsey and Southampton North, have argued the lack of UK involvement sends a "chilling message".
In the House of Commons, Labour's shadow foreign secretary Lisa Nandy questioned whether the arrest could be a retaliatory act by the government of Monaco for Mr Taylor exposing "widespread wrongdoing".
Mr Taylor was detained when he arrived in Dubrovnik for a family holiday with his wife and two children. His family has since returned home.
His wife Cindy said: "It's devastating, I had to try and be brave and we've said this is going to work out because he's done nothing wrong, and you believe in justice. And we just couldn't understand why this was happening."
A Foreign, Commonwealth and Development Office spokesperson said: "We are supporting a British man following his arrest in Dubrovnik and are in regular contact with him.
"While we cannot interfere in the legal processes of another country, our staff are in contact with the Croatian authorities about his case to seek updates."
Following Mr Taylor's evidence, SBM Offshore agreed a $240m (£186m) settlement with the Dutch authorities. It paid a similar sum to settle a case in the US.
SBM Offshore previously stated it had not influenced the extradition request.