David Cameron will today warn English voters the SNP's new powers could impact their lives . David Cameron will today risk infuriating the SNP by vowing to conduct an annual review of the fairness of the Scottish government’s policies on the rest of the UK. A Conservative government would create a new principle to ensure decisions by Holyrood do not have an ‘unforeseen detrimental effect’ for people south of the border, he will say. The Prime Minister will tell voters in England that new powers for the Scottish Parliament mean it ‘can now have a big impact on your job, your income, and investment in your area’. Mr Cameron will call the idea the ‘Carlisle Principle’ – named to reflect the sort of border communities in the rest of the UK that could be particularly badly affected by decisions taken by the Scottish government. There has been growing resentment in England and Wales at the ‘apartheid’ between those living north and south of the border in areas such as healthcare and university fees. For instance, cancer drugs have been made available on the NHS in Scotland that are not prescribed elsewhere, meaning taxpayers in England and Wales are contributing to funding them, but not benefiting. The Scottish Parliament’s new powers to cut air passenger duty could lead to air travellers and airports in the north of England being unfairly disadvantaged – and require targeted tax cuts, Mr Cameron will say. However, Scottish Nationalists are likely to accuse Mr Cameron of wanting Westminster to ‘mark the Scottish Parliament’s homework’ every year. He will also be accused of seeking to stoke anti-Scottish sentiment in the rest of the UK – and throwing fuel on the fire of Scottish nationalism. The Tory manifesto promises to introduce a principle of ‘English votes for English laws’, meaning English MPs will be given a veto over legislation relating solely to England. Under Mr Cameron’s latest plan, a formal assessment would be made by the Treasury and Cabinet Office each year of the impact of Scottish policies, including tax rates, business levies, university tuition fees and healthcare. Mr Cameron risks the wrath of Scottish National Party leader Nicola Sturgeon (pictured above) with his announcement . The Chancellor will tell MPs ‘what action is needed to make sure there is no detriment to the rest of the country’. The Prime Minister, on a campaign visit to the North West, will insist the plan will not stop the Scottish government taking the decisions it wants. ‘In the Scottish referendum, we made a clear promise to devolve more powers to the Scottish Parliament,’ Mr Cameron will say. ‘After we won that referendum, we kept our promise, and agreement was reached – for the first time – between all five of Scotland’s major parties to give the Scottish Parliament extensive new powers. ‘But as we go further in devolving powers to Scotland, we need to make sure devolution works for all the other all parts of this country too. ‘Today I want to set out a new principle – you could call it the Carlisle Principle – that we will make sure that there are no unforeseen detrimental consequences to the rest of the country from Scottish devolution.’ Boris Johnson and Sir John Major will enter the election fray this week as the Tories try to bolster their campaign. Sir John will warn of the dangers of a Labour-SNP government. The ex-premier could be deployed to speak as early as tomorrow. Later in the week, David Cameron is due to make a first high-profile campaign appearance with Mr Johnson. There are growing calls from Tory MPs for the London mayor to be ‘weaponised’. David Cameron has revealed he is locked in a high stakes battle: over ear-piercing. While contesting a general election campaign, he is also in a 'fight' with eldest daughter Nancy about when she can have her ears pierced. The Prime Minister also admitted he does not want his children to follow wife Samantha in having tattoo. In an interview with the Sun, Mr Cameron said his children 'take the mickey out of me daily', including mocking his TV and music choices. 'To them I'm just a normal dad, who they think is a bit square and sometimes embarrassing. It's very sobering to come home to after a day in the office,' he said. 'They rib me about, you know, anything from my CD collection to what I watch on TV.' Nancy is due to start secondary school in September, and wants to have her ears pierced. Mr Cameron said: 'I'm in that fight with Nancy at the moment. We'll probably reach an agreement over what age she can have them done. We're in negotiations.' His wife Samantha has a small tattoo of a dolphin on her right ankle, which she had done while travelling as a student. She has said it would 'fine' if her children copied her. But Mr Cameron said: 'I'm not a big fan. I love Samantha's tattoo, it's very small, very discreet. But I'd be a square dad and tell the children to think very carefully about it.'
A Tory government would create a new principle to review SNP policies . Prime Minister to tell English voters SNP's  powers could impact their lives . There has been growing resentment at 'apartheid' between north and south . Cancer drugs are available on NHS in Scotland but not England and Wales .