Standing on the stage at the Conservative party conference last autumn to introduce defence secretary Michael Fallon to delegates was one of the proudest moments of my life.

I told them of my remarkable journey, growing up in a close-knit Muslim family in Oldham, where I ran a kebab shop with my mother, serving in the Territorial Army and the opportunities it brought me, contesting Rochdale for the Conservatives at the 2015 election. I talked of my belief that the party would allow Britain to stand tall as a proud, outward-looking nation.

Yet eight months later I have decided to leave the party. I have today written to the Conservatives to resign my party membership. I am joining the Liberal Democrats and will campaign for Tim Farron in the final days of the election campaign. Why?

Maybe the clue lies in my words to the party conference on that day in Birmingham last October. I fervently believe that Britain must be an outward-looking country and that we are stronger inside the European Union than we will be outside it. Like many Conservatives who voted remain, I reluctantly accepted the result of last year’s referendum but expected the government would take a responsible approach to the Brexit negotiations. Instead, I have watched in horror as Theresa May has adopted an extreme version of Brexit. She is echoing Nigel Farage’s mean-spirited agenda, which will cost us jobs and put up prices. I believe it will be a disaster for Britain.

Initially, my instincts were to continue campaigning for the Conservatives, the party I joined five years ago. I had always believed they were the party of opportunity and, as an entrepreneur, I thought they were the party that would back small business. But, once the election was under way, I wrestled with my conscience.

Brexit is the most important issue facing this country and I decided I simply could not campaign for a cause I did not believe in; I could no longer support a government prepared to put our nation’s future prosperity at risk by taking Britain out of the European Union without securing any deal. The Conservatives can no longer claim to be the party of business when they are prepared to leave the world’s biggest market empty-handed; the Liberal Democrats are the only party trying to remain within it.

The decisions taken in the next couple of years will have a huge impact on us all – they will determine the money we have available to spend on our schools and hospitals; the environment around us and the air we breathe; the shape of the economy and the make-up of our society. A hardline approach to immigration might satisfy the Ukip supporters May is trying to woo for her narrow political ends, but it will not make us a wealthier, happier or more successful nation.

Immigration is blamed for so many of our country’s woes, but, as a second-generation immigrant, I reject this short-sighted approach. The real crisis facing our economy is not that immigrants are taking jobs; it’s that we don’t have a workforce equipped for the future.

An estimated 5m jobs will be displaced by technology if we don’t re-skill the next generation in the Stem subjects: science, technology, engineering and mathematics. We should be encouraging more foreign firms to invest in Britain and welcoming more overseas workers with these skills, not pulling up the drawbridge. Brexit was rejected by 75% of 18- to 24-year-olds in last year’s referendum, yet this is the generation that will be most affected by the misguided negotiating strategy May has decided to pursue.

Did anyone really vote for this narrow, negative vision of our country’s future? This nasty, Ukip-inspired version of Brexit will isolate us from our European neighbours, threatening our security and our prosperity. I believe we all should have the right to decide whether it’s a deal we want for Britain. We should be given the chance to vote in a second referendum once the full terms of the negotiations, and the implications for our country, become clear.

Only the Liberal Democrats are offering a second referendum, which is why I am delighted to be joining a party which is on the right side of this historic debate. I am passionate about getting young people more involved in politics and there can be no greater sign of political failure than ignoring the views and aspirations of an entire generation.

Labour sided with the Conservatives in voting for Brexit and failed to stand up for the rights of EU citizens in the UK. Jeremy Corbyn is not a genuine pro-European, given his long record of Euroscepticism. He has nothing to offer younger voters.

I was proud to address the Conservative party conference last October, but I am prouder still to have joined the Liberal Democrats to fight for a cause I believe in – a chance for us all to have a say in getting a deal for the whole of Britain. This will give the decision to the people in places like Oldham, where I grew up, rather than politicians in Westminster.