Plaid Cymru has pledged an extra 1,600 police officers, saying it could be delivered by handing criminal justice powers to politicians in Wales.
Liz Saville Roberts said the party would spend an extra £50m to provide an extra two officers for each community.
The party also promised to ban the use of "highly inaccurate" facial recognition technology.
Policing is overseen by the UK government, with Wales and England part of the same criminal justice system.
Plaid Cymru would need to secure the devolution of policing and criminal justice to Wales and join or form a government in Cardiff Bay to implement this plan.
Calls for the devolution of justice have also been made by the Labour-led Welsh Government.
Earlier this year a Welsh Government-appointed commission said Wales should have full control of its justice system, with powers to run policing, prisons and appoint its own judges.
Ms Saville Roberts, a Plaid Cymru candidate for the general election, said: "Police budgets have been slashed by the Tories, putting far fewer officers on the street.
"Welsh forces have been hit harder than those in the rest of the UK, due to an unfair funding formula.
"It is unacceptable that Wales is the only nation in the UK without powers over its policing and justice powers."
Plaid would create "people-centred services - from prisons to counselling to housing - to replace the present callous approach that prioritises targets over people's needs," she added.
The number of police officers in Wales fell from 6,375 in 2010 to 5,906 by March.
Under Home Office plans, 302 extra officers are to be recruited by March 2021.
Plaid claimed Wales' four forces would be in line for £25m extra from the UK government if policing was devolved.
It said this would come through the system that funds Welsh devolved services - the Barnett formula - which is calculated differently to current police funding.
Plaid pledged to add an extra £25m on top and said it would repeal the Vagrancy Act of 1824 and ensure homelessness was treated as a social problem rather than a crime, and improve victim support services.
Senior Labour politician Christina Rees said: "Yet again Plaid Cymru are announcing policies they have no prospect of being able to implement.
"This pledge is as disingenuous as Boris Johnson's promise to put fewer police back on our streets than the Tories have cut since 2010."
Jenny Rees, BBC Wales home affairs correspondent
No police force would turn down the offer of extra officers. They may quibble over exactly where they are needed, but with the budget cuts they have faced over the past decade, any investment would be welcomed.
What is interesting is the call to ban the use of facial recognition technology (AFR).
The only force in Wales currently using it is South Wales Police - earlier this year a legal challenge against its use failed.
The tech scans crowds, looking for people wanted in connection with crimes.
But it is also used to help find someone caught on camera committing a crime. For example, if I took a picture of someone causing criminal damage, police can use AFR to see if that person is in their custody database. Reducing two weeks' work to a day.
Plaid Cymru rightly say officers can be stretched covering large geographical areas with few resources and while many want the law around AFR to be reviewed, a blanket ban on this resource will be seen by others as a hindrance.