Judges' sentencing of offenders is to be televised under plans to be unveiled by the prime minister shortly, the Guardian has learned.

David Cameron is expected to make his announcement in a long-awaited crime speech, expediting the agenda even though a Ministry of Justice consultation with the judiciary into the matter has not yet begun. It is not yet known how many courts will be televised.

As part of his push for transparency in public services, Cameron will give the go-ahead to the televising of judicial verdicts but it is thought this will critically not include the process of the trial leading up to the verdict, protecting witnesses from exposure to publicity. The shift towards the televising of court proceedings has always been hampered by the spectre of OJ Simpson's trial in the US which degenerated into prime-time entertainment.

Television companies have been pressing for greater access to the highlights of court cases and a consultation on the shift was undertaken by the previous Labour government but was eventually discarded.

Now the present government has revived the plans, believing a judicial pronouncement should become more of a moment of public reckoning. Officials believe transparency would aid public understanding of the court process and the idea has gained momentum in the aftermath of the riots. Number 10 has decided to strengthen its law and order agenda in the wake of the riots, but televising verdicts is something Cameron has been minded to do for some time.

A Downing Street spokesman told the Guardian: "this is something we're looking at". But the Guardian understands No 10 is firmly committed to the plan.

The decision to go ahead comes at the end of a consultation with judges on the issue. In May, the Ministry of Justice revealed that officials would be canvassing the opinion of judges on the matter. A Ministry of Justice spokesman said: "We are considering proposals put forward by broadcasters to allow limited recording and transmission from courts in specific circumstances.

"However, before any firm proposals are developed, the lord chancellor will wish to consult on the principle of broadcasting from court with the senior judiciary."

There is a fair wind for the proposal with the director of public prosecutions, Keir Starmer, suggesting in May when the consultation was announced that he would lend the move his support. He called for greater openness and transparency in the justice system.

Then Starmer told a Society of Editors meeting: "In principle I would support a proposal that judgments, judges' closing remarks and judicial sentencing in criminal cases could be televised.

"There may be a case for going further, although I would obviously not want to promote anything that adversely affected the ability of victims or witnesses to give their best evidence to the court.

"Therefore there would need to be appropriate safeguards, particularly in cases involving vulnerable individuals, and any requests to televise any part of the court process should be subject to the judge's individual discretion."

When the country's most senior court – the supreme court in Westminster – was opened in September 2009 it was fitted with cameras. As things stand it is the only court where footage is routinely available for broadcasters on request and has been televised live.

It allows visitors to watch appeals and judgments on televisions around the building without sitting in the courtrooms, but it is seen to be a different case since supreme court hearings do not involve witnesses being cross-examined or juries.

Cameras have been allowed in some Scottish courts under tight restrictions since 1992. The appeal of Abdelbaset al-Megrahi against his conviction for the Lockerbie bombing was televised in 2002.

Writing in the Guardian in December, the head of Sky News, John Ryley, suggested the trials of six MPs who were accused of misusing their parliamentary expenses were prime examples of public interest trials that would have benefited from being televised. Last month he renewed his call for televised sentencing in an open letter to Kenneth Clarke, the justice secretary.

Labour launched a limited trial in the court of appeal in 2004.