MPs have urged the Sentencing Council not to rush through new guidelines on terrorism offences following last year's attacks in Manchester Arena, Westminster and London Bridge.

The council began working on the first set of comprehensive guidelines last year but fast-tracked production following the attacks. A six-week consultation opened in October. New guidelines will come into force this spring.

The council proposed increasing sentences for lower level offences, such as those where preparations might not be well developed or an offender has offered a small amount of help. A terrorist act can be planned quickly using 'readily available' items such as vehicles and knives. Along with online extremist material that provides encouragement, 'these offences are more serious than they have previously been perceived', the council said at the time.

The guidelines also cover terrorist attack preparation, causing or attempting to cause an explosion, collecting or sharing extremist material, raising funds for terrorism, glorifying terrorist attacks, failing to disclose information about terrorist acts, and joining or supporting a banned organisation.

Bob Neill MP, committee chair, said today: 'With recent terrorist attacks in mind, the Sentencing Council has accelerated the process of producing new guidelines to ensure that they are available as soon as possible. While I commend the urgency with which the council has responded, it must not in any way compromise the full and careful consideration of the responses that it has received to its consultation, including our own.'

A letter from the committee to the council in January highlights several concerns raised by consultation respondents. Assistant commissioner Mark Rowley, the national counter-terrorism policing lead, suggested that linking culpability with the advancement of preparation could encourage police to allow a plot to run on, putting public safety at risk. The Parole Board was worried that increasing the penalties for less serious offenders will result in them becoming more likely to commit terrorist acts when they are released. The board says: 'Most of the rest of Europe is devising interventions in the community to deradicalise less serious offenders. These programmes are more likely to be successful in the community than in prison where the influence of extremist inmates is likely to be stronger.'

Earlier this year barrister Max Hill QC, in his first annual report as the independent reviewer of terrorism legislation, said modern terrorism may require higher maximum discretionary sentences, 'but it does not in my view require the imposition of mandatory minimum sentences, which would stifle rather than promote the discretion which should be left to our judges'.