Congressional Democrats launched a fresh push for the most significant gun control in years as a former colleague who survived a mass shooting eight years ago made an emotional plea for action.

"Stopping gun violence takes courage: the courage to do what's right, the courage of new ideas," former congresswoman Gabrielle Giffords said at a Capitol Hill news conference. "Now is the time to come together. Be responsible - Democrats, Republicans, everyone. We must never stop fighting."

A bipartisan group in the House introduced a measure that would require background checks for all gun sales and most gun transfers. Federally licensed gun sellers are required to run background checks on people who buy guns, but private sellers who are not federally licensed do not.

The House measure is among the first actions taken by the newly elected Democratic majority, which pledged to make gun control a top priority. Many members were elected by making gun control a centrepiece issue, arguing for restrictions on firearms and universal background checks.

It is also a bill that garnered the support of five House Republicans, a rare feat on an issue that has cleaved along party lines. It was co-sponsored by New York's Republican representative Peter King, and supported by his colleagues Brian Mast, Fred Upton, Brian Fitzpatrick and Christopher Smith. The measure was also co-sponsored by California Democrat Mike Thompson.

Joining some of the bill's proponents was Ms Giffords, who was shot in the head eight years ago at a constituent event in Tucson, Arizona. Six people died, and 15 were wounded in that attack.

House Speaker Nancy Pelosi has signalled that the bill is a priority; she assigned the bill a low number, HR 8, to show its importance and mark the anniversary of the Tucson shooting.

"We say enough is enough by finally bringing common-sense, bipartisan background-check legislation to the floor of the House," Ms Pelosi said. "Gun violence is an epidemic that requires the energy and engagement of the entire nation."

Ms Pelosi was joined by gun safety advocates and newly installed Georgia Democrat Lucy McBath whose son Jordan Davis, a black teenager, was fatally shot by a white man in a dispute over loud music in Florida.

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Despite progress at the state level, gun control has stalled in Congress since calls for action after a shooting killed 20 children and six teachers at a Newtown, Connecticut, elementary school in 2012. After several other mass shootings in the past six years, advocates for gun control argue the country, and Congress, is finally poised to act on the issue.

"For years, that seemed like a pipe dream," Peter Ambler, executive director of Giffords, the gun control organisation named for the former congresswoman, told a group of people whose lives have been affected by gun violence. The midterm elections, he said, "delivered a mandate" to Congress to introduce gun safety legislation.

He added: "The folks running at least one of the houses in Congress know that in the face of nearly 40,000 people dying from gun violence each year, that we can no longer sit idly by and let that go on as if it doesn't matter."

Any gun control legislation will face a major roadblock in the Republican-led Senate, and the National Rifle Association (NRA) announced its opposition.

"So-called universal background checks will never be universal because criminals do not comply with the law," said Jennifer Baker, director of public affairs for the NRA. "Instead of looking for effective solutions that will deal with the root cause of violent crime and save lives, anti-gun politicians would rather score political points and push ineffective legislation that doesn't stop criminals from committing crimes."

Despite long odds in the Senate, Senator Chris Murphy and 40 other Democratic senators also introduced legislation that would require background checks for gun sales.

"We must have a national standard: no background check, no sale," Democratic senator Richard Blumenthal said in a statement. "In this past election, gun violence prevention was on the ballot and gun violence prevention won. We're now at a tipping point - on the cusp of breaking the grip of the NRA and special interests who are in the way of reasonable reforms. Beginning with background checks, we must seize this historic opportunity to move forward on common sense gun safety measures that will end the American epidemic of gun violence."