A senior German lawmaker who speaks for the ruling Christian Democratic Union (CDU) on human rights and humanitarian aid has resigned from the party, citing Angela Merkel’s “open door” immigration policy and efforts to marginalise conservatives.

Erika Steinbach, a representative of Frankfurt am Main who has been a party member for over forty years, had to ask herself some searching questions: “Would I vote CDU at the moment? No. Would I join the CDU today? No. I can only draw the honest conclusion of quitting the CDU,” she told Die Welt.

Germany has had to absorb some 1.2m migrants since the Chancellor declared there was “no limit” to the number of asylum seekers the country could receive. Frank-Jürgen Weise, head of the German Federal Office for Migration, hoped the new arrivals would bolster the German labour force, but only 34,000 have found work so far, while around 975,000 are receiving benefits.

80 per cent arrive with no documents, and thousands have been let in despite presenting papers known to be forged. Steinbach believes the authorities are actively aiding and abetting large-scale illegal immigration.

“At the Federal Office for Migration, thousands of thousands of passports have been identified as counterfeit, without the legal consequences for the respective migrants being drawn. There is a political will behind it.”

Steinbach has long been uncomfortable with Merkel’s migration policy. Her decision to finally resign seems to have been prompted at least in part by the recent terror attacks in Berlin, when a failed asylum seeker – at large in the country despite a deportation order – murdered a Polish haulier and drove his lorry into a Christmas market, killing 12 people and injuring 48.

“With migrants came not only asylum seekers, but also – as many warned from the very outset – terrorists. Our security environment has significantly deteriorated since opening the borders,” she said.

She claims that conservatives like herself have been “deliberately marginalised, step by step, even stigmatised” for raising concerns.

For now, the veteran politician has ruled out joining Alternative for Germany (AfD), a fast-rising populist movement which opposes mass immigration. She has wished them success in the upcoming federal elections, however, “so that there is finally an opposition [in parliament] again.”