The Law Commission has told the government that it could save £70m over a decade by simplifying the Immigration Rules introduced under the 1971 act, which have grown from 40 pages to over 1,100 pages over five decades.

Lawyers, judges and MPs have long complained that the rules, which date from 1973, have become too complex. Today, the commission, an independent law reform agency, says the rules should be completely redrafted to make them simpler, and reviewed twice a year. The Home Office should also introduce a less prescriptive approach to evidence required from applicants.

The commission, which has published a 232-page report following extensive consultation, says the changes would build trust, increase public confidence, lead to fewer mistakes but speedier decision-making, and cut the number of administrative reviews, appeals and judicial reviews.

On accessibility and transparency, the commission suggests dividing the content more clearly by subject matter, removing cross-references as much as possible and introducing hyperlinks to the online version to improve navigation. A more flexible approach to evidence may be suitable - for instance, a clear evidential list would work for international students, but not for family members who may have complex histories.

On administering the rules, the commission recommends an informal advisory committee to review drafting. Updates should be limited to April and October, when many statutory instruments come into force. A structured process for user feedback would rectify problems quickly.

Nicholas Paines QC, public law commissioner, said: 'For both applicants and case workers, the drafting of the Immigration Rules and frequent updates makes them too difficult to follow. This has resulted in mistakes that waste time and cost taxpayer money. By improving the drafting, restructuring the layout and removing inconsistencies, our recommendations will make a real difference by saving money and increasing public confidence in the rules.'

Barry O'Leary, a member of the Law Society's immigration law committee, said he was pleased that the commission has taken on board many points made by Chancery Lane and others: 'We welcome how far they think we should go in terms of redrafting, and acknowledging that the rules need to be suitable for the non-expert user, accurate, clear and consistent.'

O'Leary, a partner at immigration firm Wesley Gryk Solicitors, was particularly pleased that the commission has recommended a numbering system. When delving into the rules, even from the contents page, O'Leary said it is extremely difficult to know where the relevant rules are and that even the headings are unclear. 'You have to be an absolut expert to understand which parts of the rules are relevant,' he said, adding that there should 'absolutely' be a lawyer on the advisory committee.

The Home Office welcomed the report and said it would consider the recommendations carefully. A spokesperson said: 'We will deliver on the people’s priorities by introducing a points-based immigration system that is fair and easy to use, so that the UK can attract the brightest and best talent from around the world and bring overall numbers down.'