A Jewish MP broke down in tears during a Westminster Hall debate on a new Polish law about the Holocaust as he recalled the bravery of Poles who saved a relative.

Alex Sobel was paying tribute to Leopold Socha, a sewer maintenance worker in Lwów who saved the life of his great-uncle, before emotion got the better of the Labour MP for Leeds North West.

Together with his co-worker Stefan Wróblewski, Sobel said Leopold hid 21 Jewish people in the sewers, initially for money, then for free.

“They stayed in terrible conditions in the sewers for 13 months. Sadly, only ten of the group survived until the liberation of Lwów. Leopold saved the life of my great-uncle, Yehuda Mildiner. I pay tribute to Leopold and the 6,706 righteous who did so much for families like mine.”

Despite this, Sobel said he suffered a deluge of anti-Semitic abuse on Tuesday after leading the debate, only three hours after praising the “respectful” way MPs had disagreed about the controversial Polish legislation.

“This morning, in the debate on the Polish Anti-Defamation Law, I raised the issue of the law giving licence to anti-Semitic abuse,” he tweeted. “Since the debate I have been subject to a stream of abuse on Twitter. If you support the law this isn’t the way to prove it combats anti-Semitism!”

Earlier, he had said: “It was a difficult debate but it’s a clear tribute to our Parliament that those with quite different views can debate respectfully.”

The Polish government said the law, passed in February, penalises the incorrect use of phrases such as “Polish death camps” to describe Nazi facilities such as Auschwitz which were set up in Poland.

However, the law also makes suggestions of Polish responsibility for Nazi war crimes punishable by up to three years in jail.

In April, Sobel said the law “revises history and is clearly anti-Semitic”. He is one of 50 MPs to have written to Foreign Secretary Boris Johnson expressing concern.

Opponents of the law – including Israeli ministers – say it is too broad in its application and vague in its definitions, adding that it could be used to stifle historical debates about the Holocaust, and as a weapon against critics of the government.

Academics point to the right-wing ruling party’s record of attacking professors such as Jan Gross for his work examining the treatment of Jews in Poland during the war, and feel that the government will find a way to use the legislation against them.

Israeli Prime Minister Benjamin Netanyahu described the law as “baseless,” adding: “One cannot change history and the Holocaust cannot be denied.”

Israel’s national Holocaust memorial Yad Vashem said while there was “no doubt” that the phrase “Polish death camps” was a “historical misrepresentation,” the law was liable to blur the historical truths regarding the assistance the Germans received from the Polish population during the Holocaust.

Since the law was passed, both the Jewish Museum in London and the Auschwitz-Birkenau Memorial and Museum have “thousands of hate-filled emails and communications and holocaust denials,” which in part prompted Sobel to call a Parliamentary debate.