Plans for a milkshake tax officially revealed in Tory row over Boris Johnson

Boris Johnson faces his first major government row over policy before he even takes office.

Plans for a "milkshake tax" were officially revealed last night in a rushed-out Green Paper hours before Theresa May leaves office.

Such a tax would involve extending the sugar tax, which was introduced last year, to "milk based drinks" which are currently a loophole in the law.

The Green Paper said the government "may" extend the tax to milkshakes "if the evidence shows industry has not made enough progress on reducing sugar" in them.

But it's set to prompt a row with Boris Johnson, who is expected to take office as Prime Minister tomorrow afternoon.

He has already hit out at plans for a milkshake tax, vowing to halt any new "sin taxes" and the "nanny state" until there is evidence the policies work.

In Mr Johnson said earlier this month: "The recent proposal for a tax on milkshakes seems to me to clobber those who can least afford it.

Boris Johnson's leadership rival Jeremy Hunt drinking a milkshake on the campaign (PA)

"If we want people to lose weight and live healthier lifestyles, we should encourage people to walk, cycle and generally do more exercise.

"Rather than just taxing people more, we should look at how effective the so-called 'sin taxes' really are, and if they actually change behaviour.

"Once we leave the EU on October 31, we will have a historic opportunity to change the way politics is done in this country.

"A good way to start would be basing tax policy on clear evidence."

The Green Paper was finally released amid a furious Tory row over its timing.

The Green Paper also confirms plans for a ban on energy drinks for under-16s (PA)

It was dreamed up by Health Secretary Matt Hancock, who supported the measures.

But he has since become a loyal supporter of Boris Johnson , and after Mr Johnson vowed to halt the "nanny state", he reportedly tried to stop the paper's release.

Sources said the Health Secretary wanted to wait until he was sure the measures - which also include a confirmed ban on energy drinks for under-16s - had Mr Johnson's support.

The sugar tax on soft drinks was introduced in April last year, and has been celebrated by experts including the Royal College of Paediatrics and Child Health.