A lawyer and climate campaigner has accused the Supreme Court of continuing a “systemic campaign of suppression” of the environmental impact of Heathrow’s expansion, after he was fined £5,000 for contempt of court.

Tim Crosland, director of environmental campaign group Plan B Earth, was found in contempt for revealing the Supreme Court’s decision on Heathrow’s third runway a day before it was made public in December.

The 51-year-old lawyer, from Elephant and Castle in south London, previously described breaking the embargo as “an act of civil disobedience”, saying: “I have no choice but to protest the deep immorality of the court’s ruling.”

Mr Crosland arrived at the Royal Courts of Justice in London on Monday prepared to go to prison, and had even packed his toothbrush just in case.

He told the PA news agency before the hearing that he thought he might get a “short custodial sentence” of two or three weeks, adding: “Two weeks in prison is a tiny price to pay to get the truth out there.”

Mr Crosland said he broke the Supreme Court’s embargo “because of the Government’s decision not to provide honest evidence to the public” about the effect Heathrow’s proposed third runway would have on the climate crisis.

Addressing the court, Mr Crosland said: “If complicity in the mass loss of life that makes the planet uninhabitable is not a crime, then nothing is a crime.”

Three Supreme Court justices found Mr Crosland in contempt of court for his “deliberate and calculated breaches of the embargo” and fined him £5,000.

Lord Lloyd-Jones, sitting with Lord Hamblen and Lord Stephens, said Mr Crosland “wanted to demonstrate his deliberate defiance of the prohibition and to bring this to the attention of as large an audience as possible”.

The judge acknowledged Mr Crosland’s concerns about climate change, but added: “These matters do not assist the respondent (Mr Crosland) in relation to the issue as to whether there has been a contempt of court.”

Mr Crosland was also ordered to pay the attorney general’s costs of bringing the case against him.

But Mr Crosland was granted permission to appeal, which will have to be heard by a panel of Supreme Court justices who were not involved in the contempt hearing, or the five justices who heard the Heathrow case.

I’ll end up having spoken to all the judges at the Supreme Court about the climate crisis by the end of it

After the hearing, Mr Crosland joked that this meant “I’ll end up having spoken to all the judges at the Supreme Court about the climate crisis by the end of it”.

He added: “I think, in some ways, the judges are in the same position as the rest of society. They have been misled for so long and so this is a kind of judicial training, is one way of looking at it.

“So I think this is a really good opportunity to get to speak to the last remaining Supreme Court judges about the crisis and what they are going to do about it.”

Mr Crosland accused the justices of having “continued that systemic campaign of suppression” about whether the Government knew that Heathrow expansion was inconsistent with the Paris agreement.

He earlier told the court that he broke the embargo “because I believed that Heathrow expansion would breach the Paris temperature limit of 1.5C”.

He said he believed this information “was being deliberately suppressed from the public domain”, so he decided that “the antidote to that suppression was the spotlight of publicity that would follow from breaking the embargo”.

After the hearing, Mr Crosland said the courts were being “co-opted to this political economy that is driving us to destruction and they are losing their fundamental purpose, which is to uphold the law – and the first part of the law is safeguarding the right to life, safeguarding the younger generation”.

He also admitted he was slightly disappointed not to have been sent to jail, telling the PA news agency: “I think probably it would have been a good outcome in a way to get a custodial sentence.

“I had my bag packed, I had my books ready to read so I think they found a way to make this as uninteresting as possible by giving me a fine.

“That’s not really much of a story so that’s a bit disappointing.”

Mr Crosland added that being imprisoned “would have revealed some of the violence inherent in the Government’s dishonesty and that could have had quite a good mobilising effect”, but he was also “quite happy to be going home”.

In a statement after the hearing, the attorney general, Michael Ellis QC, who brought the contempt proceedings, said Mr Crosland “was wrong to have acted in contempt”.

Mr Ellis added: “His actions undermined our legal process and he acted in full knowledge of the likely consequences.

“It is right that the Supreme Court agreed and held him accountable for his actions.”