Rights group Amnesty International has condemned Lebanon for what it describes as discrimination against generations of Palestinian refugees in the country.
Palestinian refugees make up about 10% of Lebanon's population
Some 300,000 refugees are denied access to work, education, adequate housing and health care, the report says.
It calls on the government to improve conditions in 12 overcrowded camps that have housed refugees since their flight from what is now Israel in 1948-49.
But the "significant cost" that Lebanon has borne is also acknowledged.
The report says more than half registered refugees live in deteriorating camps lacking basic infrastructure on virtually the same land allocated in 1948, despite a fourfold increase in the registered refugee population.
In some households, as many as 10 people share one room, and homes are often makeshift huts lacking either ventilation or sanitation.
"The pain associated with their expulsion and the decades of living in exile is being aggravated by the systematic discrimination they suffer in Lebanon," the report says.
Amnesty carried out research in official and unofficial camps across Lebanon, including Nahr al-Bared camp before residents were forced out by fighting between the Lebanese army and a group of mainly-foreign militants.
The 24-page Amnesty report examines restrictions affecting hundreds of thousands of Palestinians, 60 years after they or their forebears fled the former Palestine.
Entitled Exiled and Suffering: Palestinian refugees in Lebanon, it calls curbs imposed by Lebanon to protect itself from the influx of Palestinians "wholly unjustified" and says they should be lifted at once.
Until recently Lebanon banned Palestinian refugees from employment in 70 professions.
Refugees are denied rights and opportunities afforded to Lebanese
The proscribed list now stands at 20 professions, but the report says the refugees still face obstacles in the job market, leading to high drop-out rates in schools.
A higher proportion of Palestinian refugees in Lebanon live in abject poverty than any other Palestinian refugee community, a situation exacerbated by restrictions on their access to social services, the report says.
"We recognise that the Lebanese authorities and people have accommodated hundreds of thousands of Palestinian refugees for almost six decades and the significant cost - economically and in other ways - this has imposed on Lebanon," Amnesty says.
It adds that additional responsibility lies with Israel and the international community to find a durable solution for the plight of Palestinian refugees "that fully protects their human rights including their right of return".
However, the report says, the Lebanese government has the obligation to immediately end all forms of discrimination against Palestinian refugees and fully respect their human rights.
The Lebanese government has not responded to Amnesty's recommendations.