Can I just make one thing absolutely clear about this. Do not be taken in by this. Once the UK government invokes Article 50, the UK will leave the EU, almost certainly within 2 years. Parliament can vote all it likes on repealing the UK EU Acts, and we can have all the referendums we want on the deal on offer, but the UK will leave the EU. There will not be a better deal offered in return for staying. Once the deal for leaving is agreed by the 27 there will be no further negotiations. The UK will be able to take it or leave it, but it will still be leaving. One it has invoke Article 50, the UK is not required to agree to anything for it to leave. If it does not agree to the leaving deal, it will leave without a deal.
The only way to stop the UK leaving the EU is for Article 50 to not be invoked, and the only way to stop that is for there to be a general election and for everyone to vote for a party that pledges that it will not invoke Article 50. This does not include either of the two main parties.
[In response to Labout Leadership contender Owen Smith misrepresenting his position by promising a referendum on the Brexit deal once it is negotiated.]