Fifty European politicians have said Scotland would be “most welcome” to rejoin the European Union as a full member if it voted for independence.

The group of mainly Green party politicians said they would help ensure any transition to full membership was “as swift, smooth and orderly as possible”.

The letter to Holyrood was signed by 26 MEPs as well as members of national and regional parliaments in Germany, Ireland, Greece, Spain and Belgium.

They said: “The question of Scotland’s constitutional future, and your relationships with the UK and the EU, are for the people of Scotland to decide. It is not our place to tell Scotland what path you should take. If Scotland were to become an independent country and decided to seek to maintain EU membership, we offer our full support to ensure the transition is as swift, smooth and orderly as possible.

“Scotland would be most welcome as a full member of the EU, with your 5 million European citizens continuing to benefit from the rights and protections we all currently enjoy.”

The show of support may be seen as a boost for Nicola Sturgeon’s campaign for a second independent referendum, given that last June Scotland voted overwhelmingly for the UK to remain in the EU.

However, the Scottish National party has been careful not to bind a second independence referendum to a return to Brussels, given some voter scepticism about the EU.

This month Spain said it would not veto an attempt by an independent Scotland to rejoin the EU, removing a key obstacle to Scottish membership.

Ross Greer, the Green MSP who organised the letter along with German Green MEP Terry Reintke, said: “There is a tremendous amount of goodwill from across the continent towards Scotland’s European aspirations. Independence is the only way to secure a European future for Scotland.

“The only thing standing in Scotland’s way to forging links with Europe is the Westminster government. Our parliament has voted to give the people a choice over their own future and no Tory government at Westminster should stand in the way of that.”

Stephen Gethins, the SNP’s Europe spokesman, said the letter showed the “depth of goodwill towards Scotland across Europe”.

Jackson Carlaw, the deputy leader of the Scottish Conservatives, said: “People might be right to smell a rat. The truth is that the SNP still can’t say whether an independent Scotland would seek to get back into the EU. This is the absurdity of the SNP position exposed. They want a referendum on independence because we are leaving the EU. But they can’t say whether they would want Scotland to go straight back in.”