By Andre Vornic BBC Europe analyst

Tensions had been rising in the Dutch Government for several days, as it became increasingly clear that relations between two populist ministers had irretrievably broken down.

Liberals leader Gerrit Zalm is opposed to Poland joining the EU

The government's collapse vindicates older fears that the LPF party of the murdered politician, Pim Fortuyn, was not ready to govern.

But today's events also raise fears for the European Union's most momentous project - eastward enlargement.

The sense of crisis had been mounting over the last week.

As well as having to cope with strained inter-personal relations, the Dutch cabinet was split over an imminent decision to enlarge the European Union by 10 members in 2004.

Political mayhem?

The move, recommended by the European Commission earlier this month, was due to be endorsed by EU governments shortly - first in Brussels next week, then at a major summit in Copenhagen in December.

Enlargement could be seriously hindered by an Irish referendum

But the two smaller parties in the coalition, the LPF populists and the free-market Liberals, had raised doubts over prospective membership for three countries in particular: Cyprus, Poland, and Slovakia.

Two of these countries pose, by most accounts, the most intractable problems.

Cyprus remains a divided island, its accession to the EU would not only import an unresolved conflict into one of the West's most coveted club, but could also threaten further political mayhem, including renewed tension between Greece and Turkey.

Poland's problem is mostly economic: it is a vast and relatively poor country, more than twice as large as the Netherlands itself, and many times less wealthy.

Welcoming it and its big, under funded farming sector into the EU implies costs that some member states are still reluctant to pay.

Liberals' opposition

While Dutch populists are not keen on enlargement in principle, the most resolute opposition this time comes from the Liberals.

Their leader, Gerrit Zalm, is a former finance minister notorious for his thrift.

He also argues that Poland's high corruption rate and weak judicial system make it unfit to join the EU at this stage.

The Dutch Government's resignation at this crucial time puts even more potential delays in the way of enlargement, which may yet be seriously hindered by a referendum in Ireland on Saturday.