The figures come as a think tank calls for social security to be pegged to the cost of living.
Universal credit is a benefit available to those out of work, disabled or below a threshold of earnings and savings.
Combined with a winding-up of older benefits and reduced employment opportunities, the number of people using universal credit across England rose dramatically over the pandemic – and has remained high since.
Provisional figures from the Department for Work and Pensions show 5,620 people were using the benefit in Monmouthshire as of March – an 11% rise on 5,076 the year before.
Sam Tims, economist at the New Economics Foundation think tank, said "inadequate levels of support" combined with low pay and insecure work was forcing people receiving benefits into difficult decisions.
In March, 39% of universal credit recipients in the area were employed.
Mr Tims urged for benefits to be benchmarked to the cost of living, to help those struggling with the current crisis.
Across England and Wales, the number of households with a member on universal credit reached a record peak in February, at nearly 4.5 million across England and Wales.
This included Monmouthshire, where 4,279 households were receiving the benefit.
Anna Stevenson, benefits expert at anti-poverty charity Turn2Us, said "far too many households" are still struggling financially.
She continued: "The Government needs to make sure support is there when people need it, and that it’s the right support to get through this crisis.
"The longer term, systemic answer, is to build an effective social security system in which people can thrive."
The number of recipients in the area peaked in February, when 5,655 were receiving the benefit.
In England and Wales 112 local authorities hit their highest ever number of universal credit recipients in March – more than 30% of all areas.