BRUSSELS (Reuters) - A group of 11 countries, led by Ireland, has made a last-ditch attempt to approve the EU's flagship policy to restore damaged nature, amid concerns the law could be shelved following EU elections in June.

The law would be among the EU's biggest environmental policies, requiring countries to introduce measures restoring nature on a fifth of their land and sea by 2030.

EU countries had planned to approve the policy in March, but called off the vote after Hungary unexpectedly withdrew its support to wipe out the slim majority in favour.

"Restoring ecosystems is essential to mitigate and adapt to the impacts of climate change, and to safeguard European food security," the 11 countries said in a letter to other EU countries' environment ministers, published on Tuesday.

"Our failure as EU leaders to act now would fundamentally undermine public faith in our political leadership," they said.

The letter was signed by Cyprus, Czech Republic, France, Denmark, Estonia, Germany, Ireland, Lithuania, Luxembourg, Slovenia and Spain.

EU countries and lawmakers agreed a deal last year, but some have warned it would impose burdensome rules on industries. Farmers have staged protests across Europe over issues including strict EU regulations.

EU diplomats said on Tuesday no country had changed its position on the law since March - leaving member states deadlocked.

Hungary, Italy, the Netherlands and Sweden oppose the nature policy, while Austria, Belgium, Finland and Poland intend to abstain. The other EU member states support the policy.

"We need one country," one EU diplomat said.

The 11 countries suggested putting forward the law for approval at a meeting of environment ministers on June 17. The European Parliament has already approved it.

That would be days after the European Parliament election - which EU officials suggested could give countries the political breathing room to support the law.

Polls suggest the election will yield an EU Parliament comprising more right-wing parties sceptical of environmental policies.

(Reporting by Kate Abnett, editing by Ed Osmond)

By Kate Abnett