By John Revill

BERN (Reuters) -Cryptocurrency campaigners have stepped up calls for the Swiss National Bank to buy bitcoin, saying the global economic turmoil triggered by U.S. President Donald Trump's tariffs made it more important for the central bank to diversify its reserves.

Supporters launched a referendum campaign in December to change the Swiss constitution to require the SNB holds bitcoin in its reserves alongside gold.

"Holding bitcoin makes more sense as the world shifts towards a multipolar order, where the dollar and the euro are weakening," said campaigner Luzius Meisser, a board member of cryptocurrency broker Bitcoin Suisse.

Buying bitcoin would free the SNB from political influence on the value of its foreign currency holdings, three-quarters of which are in dollars and euros, said Meisser, who is due to speak at the SNB annual general meeting in Bern on Friday.

"Politicians eventually give in to the temptation of printing money to fund their plans, but bitcoin is a currency that cannot be inflated through deficit spending," he said.

Switzerland has emerged as a hub for blockchain and cryptocurrency innovation, with projects such as Ethereum founded in the town of Zug – dubbed "Crypto Valley".

Currently, 11% of the Swiss population has invested in crypto assets, according to a study by the Lucerne University of Applied Sciences and Arts.

But the SNB remains sceptical, citing large price swings, liquidity concerns and security risks. It does not own bitcoin.

"Cryptocurrencies are essentially software. And we all know that software can often have bugs and other vulnerabilities," SNB Chairman Martin Schlegel told Swiss newspaper Tages-Anzeiger in March.

Yves Bennaim, an organiser of the Bitcoin Initiative, said the technology behind bitcoin was one of the most reliable and secure IT systems ever created, and was constantly improving.

Although both Bennaim and Meisser hold bitcoin, they said they were not advocating for it to boost their personal investments.

With a market capitalisation of nearly $2 trillion, the global bitcoin market is the most liquid and stable among digital assets, Bennaim said, with billions of dollars worth traded every day.

"We are not saying - go all in with bitcoin, but if you have nearly 1 trillion francs in reserves, like the SNB does, then it makes sense to have 1–2% of that in an asset that is increasing in value, becoming more secure, and that everyone wants to own."

(Reporting by John Revill; editing by Mark Heinrich)