Ireland, England and Italy closely follow with four points each, and the girls in green are currently in second place due to their points difference of +60 compared to England's +58.
Despite the setback of losing at Twickenham - their first Six Nations defeat since March 2012 - Philip Doyle's squad can stay in the hunt with a home win over Italy before a potential title decider against the French in Pau on Friday, March 14.
You can watch the full England v Ireland Women's match here on the RTÉ Player.
Ireland's record caps holder Lynne Cantwell made her 81st appearance for her country on Saturday, lining out at English rugby's headquarters some ten years after playing in a 51-10 reversal to the hosts.
The days of those heavy beatings at the hands of England are long gone as this closely-foughter encounter proved, but Cantwell was desperately disappointed to finish seven points in arrears.
Giving her reaction in the aftermath, she said: "I'm just really numb, I don't know what to think of that. Usually after we lose games, I'm upset and I'll have a cry, but I just don't know what to say about that game. We fought so hard, and I'm sure they would have been better to watch.
"Yes, we gave it everything, yes, we put our bodies on the line but that's in our DNA, that's what we do. We had it in our hands to execute a few more things and attack to put more scores on the board.
"I'm really, really disappointed with that result, even though there are silver linings. I'm just really disappointed."
Ireland fell behind to an early converted try from number 8 Sarah Hunter, with Gary Street's England side clearly determined to avenge last year's 25-0 defeat in Ashbourne.
Ireland hit back with a Niamh Briggs penalty and then scrum half Larissa Muldoon broke to the side of a well orchestrated maul for a try which Briggs converted for a 10-7 lead.
However, England went back in front before half-time as player of the match Emily Scarratt sent winger Kay Wilson over in the left corner.
It was 'a killer blow' according to head coach Philip Doyle who had to cope with losing both Briggs and powerhouse centre Jenny Murphy to shoulder injuries, while Cantwell and number 8 Heather O'Brien were sin-binned past the 70-minute mark.
A third English try from replacement flanker Marlie Packer on the hour mark proved to be the only score of a defence-dominated second half.
Despite the best efforts of the hard-running Alison Miller and Briggs, Ireland's attack was lacking at times and in the last two games they have only added two tries to the 11 they scored in their record victory over Scotland.
Doyle admitted: "The girls are sore mentally, and annoyed with certain aspects of how we played in attack, but there were a lot of positives as well as negatives.
"We didn't play enough territorial rugby and they just kept running back at us, and the English played as we expected them too. But we did well to deny them any scores from set plays or attack us on the wings."
Ireland fell foul of Canadian referee Sherry Trumbull's whistle as well, and the influence of Claire Molloy and company at the breakdown waned as a result.
"Both sides felt she (Trumbull) was a huge factor in the game. Her understanding of the breakdown confused the girls - and the English players at that - and our girls lost their confidence in that area then, which we had been targeting.
"But. I still think we can win the Championship. We just have to do it the hard way now," conceded Doyle.
On the positives they can take forward with them, he added: "We badly missed Niamh's kicking and Jenny's carrying but I am absolutely delighted with my bench, the steeliness of their defending and it was some valuable game-time for so many of them looking ahead to the World Cup (in August).
"As I told the girls, England are number two in the world and now we know we can beat them and improve significantly by August."
The Ireland Women are back in action on Saturday, March 8 when they make their historic first appearance at the Aviva Stadium as part of an Ireland-Italy double header with their male counterparts.
Tickets for the Ireland v Italy Women's game (kick-off 5pm) are available to buy here on Ticketmaster.ie. They are priced at €10 for adults and €5 for children.
After losing the Triple Crown decider in London, Cantwell says Ireland will give their all over the coming weeks in pursuit of a second successive Six Nations crown.
"We won the Grand Slam last year and that's money in the bank, an incredible achievement. But I don't think you'd be a competitive person if you didn't expect to build on that.
"You don't just stop there, there's more in us. We still have more in the tank and that's what we need to keep on striving towards. The Six Nations is still within our reach and that's what we're going for," insisted the experienced centre.