Cameron's massacre of the moderates in the cabinet has cleared the way for a Tory assault on Britain's commitment to the European Convention on Human Rights (ECHR). If there was any doubt that the nasty party has returned, it has been removed now.

In the Lynton Crosby-inspired reshuffle, the moderates, Grieve, Clarke and Hague were shifted downward or out. Their warnings and misgivings about the dangers to the liberties of British citizens – and to Britain's reputation in the world – have clearly been ignored in the rush to appease the Tory right.

Labour is fundamentally opposed to this gamble with our legal protections. We know that the UK walking away from the Convention and the European Court of Human Rights would be a betrayal of our history, and a betrayal of the British people's rights it protects.

We will fiercely defend our membership of the Convention and stand up for the rights it has protected both here and abroad. We won't sit idly by while the Tories deny our citizens the power to protect themselves against abuses by those in positions of authority. Nor will we let our influence abroad be weakened.

Just as the Tories have deserted their One Nation traditions they have buried their proud role as defenders of the rule of law. Forgotten are those conservative lawyers and political giants of the 1940s and 50s who helped draft the European Convention. Once they championed the individual against unaccountable state power and were internationalist in their outlook. Now, paralysed by the spectre of Ukip and captured by the Eurosceptic fever on their own back benches they're prepared to see our reputation and influence abroad wane and the rights of the individual undermined.

When your senior law officer – and one as widely respected as Dominic Grieve – warns that your proposals risk a "car crash" you should heed him, not sack him. By installing someone who will just tell him what he wants to hear Cameron has damaged the integrity of one of the great offices of state: attorney general.

The public deserves to know what advice Dominic Grieve gave to Cameron before being removed. They also have the right to know what the Foreign Office's assessment of the geopolitical impact of walking away from the ECHR would be for Britain. William Hague said in 2011 there'd "be no downgrading of human rights under this government" – the former Foreign Secretary claimed to understand the importance of our stance on human rights both at home and abroad. Of course he is now out of the picture.

Walking away from the European Convention on Human Rights would mean we'd join a select group of non-member nations in Europe – Belarus, widely regarded as the continent's last dictatorship.

That's not a club Labour would allow the UK to join.

And, by the way, none of what Cameron proposes would make deporting foreign criminals and terrorists easier. Human rights have become a convenient smokescreen for the UK Borders Agency failures and incompetence, which have seen the number of foreign criminals forcibly removed fall since 2010. Even if the UK left the ECHR, we're bound by many other international treaties which would come into play – the UN Convention of the Rights of the Child and the Convention Against Torture to name but two – both ratified by Tory governments. The logical next step for the Tories would be leaving the United Nations.

Instead of threatening to flout international law, wouldn't it be refreshing if today's Conservative party mentioned those who've benefited from the ECHR? Victims of crime, the disabled, the sick, the elderly. Thousands of people's lives improved in this country through human rights laws. Individual people taking on the all-powerful state and winning. You'd think a very Tory thing to do. Sadly not, under Cameron's leadership.

Labour accepts that the European Court of Human Rights needs reform. It has struggled to cope with the workload of cases since the advent of new democracies since 1989. We need reforms to speed up the really important cases where delay can cause prejudice and further tackling of the backlog of cases. We also need to improve the quality of the judges. And the court needs reminding of the importance of margin of appreciation – the flexibility it allows each individual country to implement rulings. Member states are still sovereign, and this should not be forgotten. But we won't throw the baby out with the bathwater by threatening to withdraw.

One of the Tories' favourite pastimes is to brief the press on their plans to introduce an undefined "British Bill of Rights", which would allow them to sweep away our human rights laws. But we already have a British Bill of Rights – the Human Rights Act. How would theirs differ? Which rights would they leave out? Right to life? Right to a fair trial? Right to free speech? Privacy? They need to be honest with the British people about which of their rights they no longer believe are worth protecting.

The implications for 2015 are now clear. Vote Conservative and you you'll get an unprincipled headlong rush into isolationism with some dubious international bedfellows. A government which no longer believes the court determines law and which would take powers to override your human rights.

The Liberal Democrats will insist this is a "red line", but cannot escape the fact that they are propping up a government openly preparing to rip up human rights.

Only Labour is in a position to protect individual rights against abuses by the state.

Rt. Hon Sadiq Khan MP is Shadow Secretary of State for Justice