IRN BRU’S secret recipe that has survived for more than 100 years is under threat from the Chancellor’s sugar tax.

AG Barr, makers of the soft drink, has confirmed it will be focusing more on low or no sugar drinks in the future and a spokesman for the firm was unable to say whether the famously guarded recipe would remain the same.

Irn Bru has survived a series of challenges to become one of the UK’s soft drink market leaders.

During World War Two it was forced out of production because it was not a designated “standard drink”.

It was then forced into a name change in 1946 from Iron Brew, because it was not brewed.

In the latter half of the 20th century it faced increased competition form big global brands like Coca-Cola.

But A.G Barr persevered with the same recipe and by deploying clever marketing, the product grew to be a major player that exports to countries around the world.

Irn-Bru contains 35g of sugar in each 330m can and would fall foul of the sugar levy when it come into force in 2018.

The firm insisted it is awaiting the outcome of a consultation on the tax but said it is looking at “reformulation and innovation” and is planning to increase the sugar free drinks in its portfolio to 66 per cent from the current 40 per cent.

Barr’s has been heavily reliant on Irn Bru for its revenue accounting for 40 per cent of its latest £250m turnover.

It also stated “brand strength” would help it weather the storm of the sugar tax, indicating it believed loyalty of Irn Bru consumers would see sales remain high.

Until the full details of the sugar levy are revealed Barr is unable to guarantee Irn Bru will remain untouched but will reposition its business towards low sugar brands out with the tax

Roger White, A.G Barr chief executive, said “The exact details of the levy are still unclear and we will play an active role in the consultation process with the government.

“Consumer behaviour is changing and we have been responding accordingly through a comprehensive reformulation and innovation programme.

When asked if the Irn Bru recipe and sugar content would remain untouched, a spokesman for the firm was declined to give a definitive answer and said Barr wanted to wait for the outcome of the consultation.

Mr White said: “Although the details of the Chancellor’s proposed soft drinks levy are still to be consulted upon, we believe our combination of brand strength, ongoing product reformulation and consumer driven innovation will allow us to minimise the financial impact on the business at the proposed point of implementation in April 2018.”

Irn Bru’s unique identity and quirky marketing strategy will be crucial according to retail experts.

Leigh Sparks, Professor of retail studies at Stirling University said: “Irn Bru is clearly a long established iconic Scottish brand and it has played on its Scottishness as well as its distinctiveness.

“When the sugar tax hits its core brand it will respond with some changes, but it is not being singled out and it already has diet Irn Bru and other low sugar brands.”