Thousands more prisoners will be able to make phone calls from their cells under Government plans to tackle violence and re-offending.
The measure aims to boost rehabilitation by helping inmates maintain family ties, tackle the flow of illegal mobiles and reduce tension on wings.
Currently, in-cell phones are installed in 20 prisons in England and Wales.
In July, ministers announced that the scheme would be extended to a further 20 establishments.
Under a further £10 million roll-out, funded by additional money allocated to prisons in the Budget, the number of jails with phones in cells will rise to 50 by March 2020.
Announcing the expansion, Justice Secretary David Gauke said: "At this time of year more than any other we're reminded of the importance of family, and there can be few groups that this applies to more than prisoners.
"In-cell telephones provide a crucial means of allowing prisoners to build and maintain family relationships, something we know is fundamental to their rehabilitation.
"Introducing them to more prisons is a recognition of the contribution I believe in-cell telephones make to turning prisons into places of decency where offenders have a real chance to transform their lives."
Potential security benefits form part of the reasoning behind the decision to extend the availability of in-cell landline phones.
The Ministry of Justice (MoJ) said they help the Government's wider drive to bring stability to the prison estate by reducing tension which can arise from queuing to use communal phones, and by providing an alternative to illicit mobiles, which fuel crime and violence,
Authorities have identified the illegal use of mobiles as one of the most significant threats faced by jails.
In the 12 months to March, there were 10,643 incidents where mobile phones were found in prisons, a 15% increase compared with the previous year.
Other measures taken to stop handsets getting into prisons include the introduction of body scanners and improved searching techniques.
In-cell phones, which allow inmates to make calls in private at a time which fits with their families' schedules, also form part of the Government's attempts to drive down re-offending, which is estimated to cost society £15 billion a year.
Helping prisoners preserve relationships with their loved ones will improve their chances of rehabilitation, the MoJ said.
The department added that the phones also provide easier access to support services such as the Samaritans and MIND, therefore reducing the risk of self-harm.
All calls on in-cell phones are recorded and can only be made to a small number of pre-approved numbers.
In the event that they are suspected of being used for criminal activity, calls can be monitored, and governors have the power to remove phones from those who have misused them.
Prisoners will continue to pay to make calls on in-cell phones.