Theresa May’s call for the United Kingdom to withdraw from the European convention on human rights is more about her own prospects in the Tory leadership contest than what is best for the country. The ECHR, formed following Winston Churchill’s 1948 call for a European “charter of human rights” after the horrors of the Nazis and the second world war, has long been a scapegoat for Conservative cabinet ministers. But all the institutions of the European Union regard the ECHR as the basic standard for human rights. They refer to it in the way they legislate, in the way the European court of justice makes decisions and in the way the commission fashions directives. The call to leave the ECHR and stay in the EU makes no practical sense. So we have to make clear the real reason for taking this stance; shameless positioning for a bid to replace David Cameron at the head of the Tory party.

Apart from that, May’s speech was an important one. She set out convincing and coherent reasons why it is so crucial that we vote to remain part of the EU. She is right when she says that “remaining a member of the European Union means we will be more secure from crime and terrorism”.

But the price of staying in should have nothing to do with our membership of the ECHR. That false argument should be wholly rejected. We should focus on what is best for Britain, not just what is best for May’s leadership prospects. And it is best for Britain to stay a strong and influential member of the EU and for our citizens to stay protected by the rights afforded to us by our membership of the ECHR.

The divided message from the Conservatives helps no one. Britain’s home secretary saying she wants to leave the convention sends a shameful message from one of the great offices of state of a nation that goes round the world promoting human rights.

Michael Gove, the justice secretary and one of the leaders of the leave campaign, May and Cameron should all give clear statements that they will not campaign to withdraw from the ECHR, whatever the result of the EU referendum on 23 June.

In contrast Labour’s position is clear. We are committed to the UK remaining a signatory of the ECHR and committed to campaigning for a remain vote. As we have consistently done in the past, we will robustly defend any attempt to diminish human rights protections in this country or abroad. But right now our focus is campaigning to keep Britain in the EU.

We are better off inside the EU. It brings us jobs, growth and investment and protects British workers and consumers. Leaving would put that at risk and diminish Britain’s influence in the world. And as May herself set out in her speech, we are safer in.

During her term as home secretary we have been able to remove thousands of criminal suspects to other EU countries as a result of the in European arrest warrant (EAW). The EAW, pushed through in 2004 under a Labour government, means that over 600 criminals were sent by EU partners back to British soil to face justice here, including the failed London bomber Hussain Osman, brought back after fleeing to Italy in 2005 and now serving a life sentence for terrorism.

We are better off, stronger and safer together. Both Boris Johnson and May know this but their Tory leadership prospects have clouded their judgments. Whether it is attacking the ECHR or complaining about a bust in the Oval Office, they both posture and purport to defend Churchill’s memory while at the same time undermining their claims by trashing one of his most significant legacies.

• The headline was amended on 27 April 2016. It originally referred to “EU human rights law”. The ECHR is not related to the EU.