Germany’s top court on Wednesday instructed the country’s coalition government to postpone further proceedings regarding a proposed heating law, in a blow to parliament’s plans to phase out fossil fuel heating systems.

The Federal Constitutional Court ruled in favour of conservative lawmaker Thomas Heilmann of the Christian Democratic Union, who argued in an injunction that the government needed more time to deliberate on the bill, which aims to make the country’s building sector more environmentally sustainable. He argued that rushing the bill through parliament violated his constitutional rights as a parliamentarian.

“The deliberations on [the heating law], which were shortened as much as possible by parliament, do not allow the conceptual weaknesses of the law to be identified and changed,” Heilmann said in a tweet. He added that the government “is ruining the heating transition with a last-minute legislative package and an unconstitutional procedure”.

The decision to postpone final deliberations, which were set to take place at the end of this week, was passed by five votes to two.

Last week, leaders of Germany’s three ruling parties, the SPD, the Greens and the Free Democrats Party (FDP), reached an agreement on the details of the regulations within the proposed law, which included subsidies for low-emission boilers. The coalition had said previously that it wanted to move the bill through parliament quickly, with a final vote planned before summer recess this week.

In April, the government finalised plans to limit the use of fossil fuel heating systems in new installations. The law states that by 2024, all newly installed heating systems must use a minimum of 65% renewable energy.

The Greens have been pushing for ambitious climate targets, while the pro-business FDP insist on greater scope for heat pump alternatives.