Tony Blair at the despatch box during prime minister's questions

The drinks giant Diageo has changed Cardhu whisky from a single malt into a blend of malts but is continuing to sell it under its old name.

Moray MP Angus Robertson raised the dispute during prime minister's questions in the Commons.

Tony Blair said he was not an expert but that he would look into the issue.

Diageo stopped bottling the Cardhu single malt, which is made at Knockando, in Moray, earlier this year.

The company said demand from markets in Spain, Greece, Portugal and France was outstripping supply and it had no choice but to blend in other malts.

I am not entirely sure this is a matter for government, at least I sincerely hope it is not a matter for government. Tony Blair

However, rival firm William Grant & Son have complained that the "new" whisky should not be called Cardhu and the dispute has threatened to split the whisky industry.

Mr Robertson asked: "Does the prime minister support the ongoing cross-party efforts in the All-Party Scotch Whisky Industry Group to find a solution and enhance the good name and reputation of this important product at home and abroad?"

Mr Blair replied: "To be absolutely frank, I am not an expert on how whisky is designated as opposed to drunk.

"It is true that of course we have frozen duty on whisky for many years and that is important.

"But as for this issue to do with the redesignation of Cardhu, I will look into that.

Angus Robertson: "Unity and integrity threatened"

"I am not entirely sure this is a matter for government, at least I sincerely hope it is not a matter for government.

"In any event, I will certainly study the comments of the all-party parliamentary group on Scotch whisky."

The group is due to meet Diageo managers on Thursday, the second time in just over a week that talks have been held in an attempt to defuse the row.

Speaking after prime minister's questions, Mr Robertson, an SNP MP, said: "This is a hugely serious issue, which is threatening the unity and integrity of one of Scotland's most important industries.

"I welcome Tony Blair's response and his interest in the problem.

"Now that we have focussed attention on the problem at the very highest level of government, I hope and believe we can use this to our advantage by getting the different parties in the dispute to agree to a solution."