Justice secretary Chris Grayling has attempted to see off a possible rebellion on judicial review reform with a late amendment.
The House of Commons is due to vote on Monday on amendments to the Criminal Justice and Courts Bill that were laid down by the House of Lords earlier this month.
One of the Lords amendments relates to interveners in judicial review not automatically paying their own costs.
Grayling submitted his own amendment yesterday which grants a small concession to the presumption of interveners paying costs.
The justice secretary said interveners would be liable for costs if their evidence and representations have not been 'of significant assistance' to the court.
Costs will also be imposed if the intervener has behaved 'unreasonably' and if a significant part of their evidence is on matters that are not necessary for the court to consider.
MPs will have the chance to vote on this amendment and the changes proposed in the Lords.
But the Bar Council, one of three representative groups who wrote to MPs this week asking them to vote against the government, told the Gazette that Grayling's concession is an 'empty gesture'.
The issue of costs would still be judged after the event, with interveners having to judge in advance what impact their evidence is going to have.
A Bar Council spokesman said: 'It will still be a gamble for charities and NGOs to intervene in judicial review cases. The government amendments do not address the concern that charities and non-governmental organisations, who try to assist the court at their own expense and only ever with the express permission of the judge, will feel a chilling effect.
'These proposed changes mean interveners will have to correctly second guess whether or not a judge will agree their intervention has been of 'significant assistance' or else face prohibitive legal costs.'
He added that judges already have the power to reject an intervention if they feel it will not be useful, with the government amendment 'trying to solve a problem which does not exist'.