Labor remains ahead of the Turnbull government in the national political contest, and a majority of voters believe political parties should not change leaders before elections, according to the latest Guardian Essential poll.

The latest fortnightly survey of 1,022 respondents sees Labor ahead of the Coalition on the two-party preferred measure 51% to 49%, which is the same result as the last survey. The national poll lead follows the ALP holding its terrain in crucial byelection contests in marginal seats in Queensland and Tasmania at the weekend.

With the super Saturday contests putting leadership of the major parties back in the daily news headlines, voters were also asked to agree or disagree with a number of statements about leadership of Australia’s major political parties.

Reflecting the impact of more than a decade of leadership instability in Canberra, the picture the poll returned was mixed. A majority, 64%, agreed with the statement political parties should not change leaders before elections.

But 46% agreed parties had the right to change leaders, and 56% agreed that political parties should replace a leader who was unpopular.

Voters were also asked to nominate in this survey who was best to lead the Liberal and Labor parties.

The prime minister led the field for the Coalition, with 28% (up 4% since April), while 16% nominated the party’s deputy leader, Julie Bishop.

Tony Abbott – who maintains a high public profile and is a frequent critic of government policy – was down one point on 10%.

Two other conservatives who have expressed their ambitions publicly, Scott Morrison and Peter Dutton, were well back on 2% and 5% respectively.

The prime minister was also the pick of 51% of Coalition voters, a six-point jump since April, while 11% nominated Bishop and 11% Abbott. Abbott’s support among Coalition voters is down six points since April.

While Turnbull has clear ascendancy over all his party room rivals, it’s a different picture on the Labor side.

The Labor leader Bill Shorten and the prominent leftwing frontbencher Anthony Albanese – who floated an alternative manifesto in the run-up to the byelection contests – were neck-and-neck in the latest survey. Shorten was nominated by 19% of voters, as was Albanese.

Albanese’s ranking is up six points since April. Labor’s deputy leader, Tanya Plibersek, was nominated by 12% of the sample.

Among Labor voters, Shorten pulled ahead of Albanese, with 37% (up 3%) preferring him, 17% (up 2%) Albanese and 13% (down 2%) Plibersek.

Labor’s strong performance in the weekend political contests has settled the bubble of leadership instability within the opposition but put the Coalition under renewed pressure, given the LNP’s weak showing in Queensland – the state that will determine the outcome of the next federal election because of its high proportion of marginal seats.

The outcome of the various byelections, triggered by the last vestige of federal parliament’s dual-citizenship crisis, have also served to push back a federal election until 2019.

The prime minister is also under internal pressure to dump the government’s proposed tax cut for Australia’s largest businesses, which the ALP used as a campaign weapon in the Queensland seat of Longman. The tax cut was the focal point of a substantial negative television and radio advertising campaign.

This fortnight’s poll asked voters to rank policies, leaders and candidates in determining their votes in election contests. A majority of 55% ranked policies as very important in deciding who to vote for, while 28% said leaders, and 27% the local candidate.

Voters were also asked questions about the attributes of the major political parties. According to the data, the Liberal party’s main attributes are – too close to big corporate and financial interests (67%), will promise anything to win votes (64%) and out of touch with ordinary people (64%).

Since the question was asked in November last year, voters think the Liberal party is less divided, has a good team of leaders, and is clear about what it stands for.

On the Labor side the main attributes were – will promise anything to win votes (68%), looks after the interests of working people (57%), divided (56%) and moderate (53%).

Possibly reflecting the internal tensions reported in the lead up to the super Saturday contests, voters think Labor is more divided than they did last November, less extreme, and there’s been a five point drop in “too close to the big corporate and financial interests”.