The UK's withdrawal from the European Union and its impact on primary dealers in government bond markets is a big concern for euro zone governments.
This is according to officials from the Irish and Finnish debt management agencies.
The numbers of primary dealers - banks that are appointed by governments to buy their debt at auctions and sell them on to investors - have fallen in recent years.
Regulatory pressures have forced banks to re-examine their involvement in various sectors including this one.
Fewer primary dealers could increase constraints in government bond markets and ultimately make it more expensive for countries to borrow.
Brexit could add to the hurdles of being part of this business if London-based banks have to relocate parts of their business to continental Europe to stay in primary dealerships.
"For me the biggest concern (over the next 12 months) would have to be Brexit and the effect it will have on markets," Anthony Linehan, deputy director, funding and debt management, at the National Treasury Management Agency, said.
He made his comments at a Euromoney conference in London.
"There could be quite a lot of change if our primary dealers have to relocate their legal entities around Europe," Mr Linehan said.
"We are now two years on from the referendum and it doesn't strike me that we have achieved an awful lot in those two years," he added.
Many of the banks who act as primary dealers for European governments are based out of London.
Depending on the final Brexit deal, they may be forced to move some operations out of Britain's capital city if they want to hold on to that business, sources have told Reuters in the past.
Scotiabank last month became the latest firm to resign as a primary dealer in Britain.
The concern for euro zone governments is that some of them may choose to exit the business altogether instead, said Teppo Koivisto, director of finance at Finland's state treasury.
"We are having discussions with the banks about this issue, we want to make sure we have all our primary dealers working with us," he told Reuters on the sidelines of the conference.
"At the moment we don't know how they are going to solve the riddle - but we will have to see how the Brexit negotiations go," he said.