Constitutional reforms will strengthen hand of President Daniel Ortega, who is seen by critics as increasingly authoritarian

Nicaragua's parliament is poised to approve a package of constitutional reforms that will remove presidential term limits and strengthen the hand of the Sandinista leader, Daniel Ortega.

Critics fear the changes, which would also allow members of the military to hold civilian government posts, are a sign of increasingly authoritarian tendencies.

A plenary session of parliament voted 64-26 in favour of the bill, which is the most controversial and wide-ranging set of constitutional reforms in over a decade.

The reforms will come into effect if approved a second time early next year, which looks certain to happen: the Sandinista National Liberation Front (FSLN) has more than the 60% of MPs needed to change the constitution.

Supporters say the measures are designed to rationalise governance and incorporate into law several changes that have already taken place in recent years.

Among the measures under consideration are the removal of constitutional prohibitions on a president serving more than two terms and running for consecutive elections.

Ortega has already effectively steamrollered this curb – introduced in 1995 under the non-Sandinista government of Violeta Chamorro – by winning a third term in 2011. The latest reform will enable him to run again.

He is following the lead of Hugo Chávez in Venezuela, Evo Morales in Bolivia and Rafael Correa in Ecuador, who all amended their constitutions or secured judicial backing to let them run again. Moderate leftwing leaders in Brazil and Uruguay have declined to take such steps.

The bill will also allow senior officials, including supreme court justices and supreme electoral council magistrates, to stay in their posts indefinitely, beyond their constitutionally defined term limits, if parliament fails to elect their successors. This is another practice Ortega effectively introduced by presidential decree in 2010.

The military, potentially, will be able to play a wider role in running the nation. Officers will be allowed to hold unelected government posts, and limits will be removed on the number of times the head of the army can be re-elected. The revised constitution will recognise local "family cabinets", a system of grassroots councils set up by the government to enhance democratic participation that has often been criticised as a means for the FSLN to exercise power at a local level.

Ortega said the measures were the result of extensive consultation. "I am sure that, when this reform is finally passed in the second legislative session next year, there will be greater tranquillity, more security, more peace, more joyfulness and more hope among the Nicaraguan people," he said during a speech marking the graduation of police cadets.

Gerardo Rodríguez, president of the Managua appeals court, said the reforms simply reinforced changes of the past decade and strengthened the state's ability to enhance social development. "No concentration of power can be perceived in any of the reforms," he told El 19 Digital, a Sandinista publication.

However, critics said the state was being militarised and Ortega was strengthening his grip on power at the expense of neutral institutions and democratic opposition. The former Sandinista comandante Hugo Torres told the Guardian the army's efforts to professionalise could be undermined, leading it to become a repressive body at the service of the government.

"Ortega is attracting the army, flattering it through this reform by giving it a greater scope of action, allowing it more prerogatives, allowing it to interfere in the civil sphere," he said.

Torres said constitutional reform was the last element Ortega needed to consolidate his control and to build a "corporatist state", having already secured influence over the police force, built alliances with business, taken control of most of the media and unions, strengthened his family's grip on the ruling party and amassed economic power.There has been growing concern about the government's concentration of power since FSLN won a landslide victory in elections in 2011 that were questioned by the European Union electoral observation mission.

Ortega has proved himself a political survivor. He took power after the Somoza dictatorship was toppled in 1979 and oversaw a government that introduced popular programmes for education, health and poverty alleviation. Despite losing elections in 1990, 1996 and 2001, he remained leader of his party and bounced back from several setbacks to secure another victory for the FSLN in 2007.

His traditional caudillo style of leadership – a political strongman with a paternalistic but close relationship with the grassroots – has generated loyalty to him as a party figurehead and a sense that he is strong and powerful enough to get things done. But there are concerns that he and his government are growing more intolerant of criticism. Many were alarmed in June when the police stood idly by as a group of pro-government supporters violently broke up a demonstration in support of pension rights for the elderly.

Opponents say Ortega is repeating the mistakes of past leaders who ignored criticism and steadily built personal power. "With these constitutional reforms we're taking Nicaragua into another cycle of the violence we already know. Somoza did that and we know where he ended up," Eliseo Nuñez, an Independent Liberal party parliamentary representative, told Envio magazine.

But for the most part Nicaragua remains peaceful and Ortega remains popular. According to a CID-Gallup Latin America poll conducted in September, the FSLN was the most popular party on 52%, a long way ahead of any other parties. Free education, free healthcare and programs to improve homes have been gratefully received and for many people their continuation is a more immediate concern than constitutional reform.

In Managua's Roberto Huembes market amid the bustle of preparations for the traditional Immaculate Conception festivities, Sebastian Zamora, a stallholder, said he saw nothing sinister in the reforms. "It's normal," he said. A bigger priority for him was social policy: "The government is doing a lot to help those in most need. It has increased their access to health and school and everything is slowly improving."

But there was also scepticism about who would profit from changing the constitution. Maria Sanchez, a fruitseller, complained that the government wanted to control everything, and dismissed the reforms as "just for them, for their benefit. We're not going to benefit from them at all."

Additional reporting by Gareth Richards