Parents could face a fine or prosecution if they take their children out of school for even half a day without permission following a landmark ruling by the UK's highest court.

Five Supreme Court justices unanimously ruled against father Jon Platt who took his daughter to Disney World during school term-time in a decision which will have a major impact on schools and parents across the country.

In a judgment clarifying what "regular" attendance at school means, they allowed an appeal by Isle of Wight education chiefs against an earlier ruling that Mr Platt had not acted unlawfully.

The panel of judges, including the court's president Lord Neuberger, declared Parliament's intention was that the word "regularly" means "in accordance with the rules prescribed by the school".

This effectively means mothers and fathers should not take their child out of lessons at any point without the headteacher's approval.

The judges pointed out there are exceptions to that rule, which include religious holidays and sickness .

Speaking after the ruling was given, Mr Platt said he was "not at all surprised" at the judgment.

He said: "I'm pleased that they acknowledged the judgment doesn't go on to say what the school rules should be.

"Schools need to think very carefully about what these rules should be.

"Some have policies that mean that every day missed is a criminal offence."

Mr Platt's case now has to return to the magistrates' court in the light of the ruling on Thursday.

He said he had "no intention" of pleading guilty when the case goes back to the court.

Lady Hale, announcing the decision, emphasised the case was not about what the rules should be "or how much discretion the headteacher should have to authorise absence".

She added: "That is a matter for the appropriate authorities."

The council prosecuted Mr Platt after he refused to pay a £120 penalty - under the fixed penalty procedure a parent can avoid prosecution if they pay.

Magistrates said he had no case to answer, and the High Court later ruled that he was not acting unlawfully because his daughter had a good overall attendance record of more than 90%.

The decision caused a surge in term-time bookings all over England.

At a Supreme Court hearing in January, the local authority, backed by the Education Secretary, argued that a child's unauthorised absence from school ''for even a single day, or even half a day'' can amount to a criminal offence.

But a QC for Mr Platt described the submission as a new and radical interpretation of the law which was absurd and would ''criminalise parents on an unprecedented scale''.

After the Supreme Court ruling, Isle of Wight Council said in a statement: "The Supreme Court's judgment provides much-needed clarity about what constitutes regular attendance at school, to schools, parents and local education authorities.

"The Isle of Wight Council will ensure it continues to apply its code of conduct in relation to school absence and in accordance with this judgment."

Lady Hale said that "given the strictness of the previous law, Parliament is unlikely to have found it acceptable that parents could take their children out of school in blatant disregard of the school rules, either without having asked for permission at all or having asked for it, been refused".

She added: "This is not an approach to rule-keeping which any educational system can be expected to find acceptable.

"It is a slap in the face to those obedient parents who do keep the rules, whatever the cost or inconvenience to themselves."

Prime Minister Theresa May said: "What the Supreme Court has done is endorse the current position, which is right, which is that we recognise - and they've recognised - the importance of children being in school and getting the most out of their education but also recognise that there may be exceptional circumstances where a child needs to be taken out of school during term time and it's right that the individual headteacher has that flexibility to make that decision. I think that is the correct balance."