New measures to bar tens of thousands of foreign workers from outside Europe coming to work in Britain as the recession bites deeper were outlined by the home secretary, Jacqui Smith, today.

The package includes possible moves to prevent the families of skilled migrants working in Britain and restricting skilled migrants to taking jobs only in occupations with shortages.

It represents a significant tightening of the new Australian-style points-based immigration system only four months after its introduction last November in the face of mounting "British jobs for British workers" protests and fears that the far-right British National Party, will win seats for the first time in June's European elections.

The government has already banned the legal movement of unskilled economic migrants from outside Europe to Britain and the package outlined by the home secretary represents the first move to cut the number skilled migrants coming to work.

Smith signalled that raising the qualification levels for tier 1 – the most highly skilled migrant route – could cut the numbers from 26,000 to only 14,000 a year. The new criteria will require a master's rather than a bachelor's degree and a job offer with a minimum salary of £20,000 rather than £17,000.

Smith has also asked the government's migration advisory committee to assess the economic case to restrict skilled workers under tier 2 to shortage occupations only. This could cut the numbers from an estimated 80,000 to only 20,000 to 40,000 a year.

The migration advisory committee, chaired by LSE professor David Metcalf, has also been asked to assess the economic impact of banning the spouses and other dependants of foreign workers from taking jobs in Britain. This move could also affect tens of thousands of people who come to work each year mainly from India, Pakistan and parts of Africa.

"These measures are not about narrow protectionism," Smith said. "Just as in a growth period we needed migrants to support growth, it is right in a downturn to be more selective about the skill levels of those migrants, and to do more to put British workers first."

The home secretary said the action she was taking "to be more selective" combined with the economic circumstances. As migration levels tend to fall during periods of recession she expected the number of migrants outside of Europe to fall during the next financial year.

The points-based immigration system does not cover the movement of workers from within the European Union to Britain but official immigration figures to be published on Tuesday are expected to confirm that the number of Poles and other eastern Europeans coming to work continues to fall, especially since the decline of the pound against the Euro.

Other measures outlined today/yesterday include:

• Employers must advertise tier 2 skilled jobs in JobCentres before they can bring in a worker from outside Europe.

• Migration advisory committee to assess economic contribution made by dependants of those who come under the points-based immigration system and their role in the labour market.

• Each shortage occupation declared by the committee to trigger a skills review of the British labour force and how they can be developed to meet the shortage.

Damian Green, the Conservatives' immigration spokesman, said Smith was just "tinkering around the edges" of the system and said if she wanted to control migrant numbers she should introduce an annual limit.