Prisoners were too comfortable to want to escape, Mr Travis said
Inmates are so comfortable in jail that they do not want to escape, a prison officer union leader says.
Glyn Travis of the Prison Officers Association says inmates are happy to stay inside because they can get hold of drugs, mobile phones and even sex.
He said a dealer regularly broke into a Yorkshire prison by using a ladder to enter cell windows - but no inmate used the ladder as a means of escape.
The Prison Service said the prisoners were never in a position to escape.
Mr Travis said the authorities only became aware of the security breaches at low-security category C Everthorpe prison, near Brough, East Yorkshire, in January.
"The prisoners didn't take this opportunity because we believe life is so cushy within the prison system," he said.
Mr Travis said there had been similar incidents in other prisons and he knew of cases of prostitutes entering open jails to service clients.
He added; "We have got no-go areas in certain prisons because prisoners have got complete control. There is not sufficient staff, there is no interaction between staff.
"We have got a serious crisis in our prisons today."
Mr Travis blamed a shortage of prison officers and relaxed regimes, where prisoners enjoyed satellite television and video game consoles.
He said that efficiency savings had reduced staff levels and the supervision of prisoners.
"Drugs are coming into prisons at a rate that's so dramatic that drugs in prison are actually cheaper than on the outside," he added.
A spokesman for the Prison Service said: "During the incident, at no time were prisoners out of their cells or able to access any other areas of the prison.
"Immediate action was taken with extra fencing, the removal of trees, extra CCTV cameras, and the transfer of the offender involved to another establishment."
Juliet Lyon, director of the Prison Reform Trust, said prison officer numbers had failed to keep pace with the increase in inmates.
"As our overcrowded jails turn into warehouses, staff are being pushed into acting as turnkeys.
"There is far too little useful work in prison, but the idea that jails are cushy is blown away by the appalling levels of suicide and self-harm."
In 2007, 92 prisoners committed suicide, compared with 67 the previous year, according to government figures.
And there were 23,420 incidents of self-harm in 2006 in prisons in England and Wales, figures obtained by the Prison Reform Trust show.
Conservative leader David Cameron said there needed to be a "big change" in Britain's prisons.
"We live in a topsy-turvy world where we've now got people trying to break into prison to sell drugs," he said.
"Prison should be a place where you are put to work, where you make reparations to your victims and payback money to society and reform your character before you get out.
"We're a long way from that and we need a really big change in our prisons."
A spokesman for the Ministry of Justice said prison conditions were appropriate.
"The punishment of the court is loss of liberty - harsh regimes do not lead to rehabilitation or a reduction in reoffending," he said.